1Catalyst::Manual::TutorUisaelr::C0o4n_tBraisbiuctCCeaRdtUaDPl(ey3rs)lt:D:oMcaunmueanlt:a:tTiuotnorial::04_BasicCRUD(3)
2
6 Catalyst::Manual::Tutorial::04_BasicCRUD - Catalyst Tutorial - Chapter
7 4: Basic CRUD
8
10 This is Chapter 4 of 10 for the Catalyst tutorial.
11 Tutorial Overview
13 1. Introduction
15 2. Catalyst Basics
17 3. More Catalyst Basics
19 4. 04_Basic CRUD
21 5. Authentication
23 6. Authorization
25 7. Debugging
27 8. Testing
29 9. Advanced CRUD
31 10. Appendices
33
35 This chapter of the tutorial builds on the fairly primitive application
36 created in Chapter 3 to add basic support for Create, Read, Update, and
37 Delete (CRUD) of "Book" objects. Note that the 'list' function in
38 Chapter 3 already implements the Read portion of CRUD (although Read
39 normally refers to reading a single object; you could implement full
40 Read functionality using the techniques introduced below). This
41 section will focus on the Create and Delete aspects of CRUD. More
42 advanced capabilities, including full Update functionality, will be
43 addressed in Chapter 9.
44 Although this chapter of the tutorial will show you how to build CRUD
46 functionality yourself, another option is to use a "CRUD builder" type
47 of tool to automate the process. You get less control, but it can be
48 quick and easy. For example, see Catalyst::Plugin::AutoCRUD,
49 CatalystX::CRUD, and CatalystX::CRUD::YUI.
50 Source code for the tutorial in included in the /home/catalyst/Final
52 directory of the Tutorial Virtual machine (one subdirectory per
53 chapter). There are also instructions for downloading the code in
54 Catalyst::Manual::Tutorial::01_Intro.
55
57 Our initial attempt at object creation will utilize the "URL arguments"
58 feature of Catalyst (we will employ the more common form-based
59 submission in the sections that follow).
60 Include a Create Action in the Books Controller
62 Edit lib/MyApp/Controller/Books.pm and enter the following method:
63 =head2 url_create
65 Create a book with the supplied title, rating, and author
67 =cut
69 sub url_create :Local {
71 # In addition to self & context, get the title, rating, &
72 # author_id args from the URL. Note that Catalyst automatically
73 # puts extra information after the "/<controller_name>/<action_name/"
74 # into @_. The args are separated by the '/' char on the URL.
75 my ($self, $c, $title, $rating, $author_id) = @_;
76 # Call create() on the book model object. Pass the table
78 # columns/field values we want to set as hash values
79 my $book = $c->model('DB::Book')->create({
80 title => $title,
81 rating => $rating
82 });
83 # Add a record to the join table for this book, mapping to
85 # appropriate author
86 $book->add_to_book_authors({author_id => $author_id});
87 # Note: Above is a shortcut for this:
88 # $book->create_related('book_authors', {author_id => $author_id});
89 # Assign the Book object to the stash for display and set template
91 $c->stash(book => $book,
92 template => 'books/create_done.tt2');
93 # Disable caching for this page
95 $c->response->header('Cache-Control' => 'no-cache');
96 }
97 Notice that Catalyst takes "extra slash-separated information" from the
99 URL and passes it as arguments in @_ (as long as the number of
100 arguments is not "fixed" using an attribute like :Args(0)). The
101 "url_create" action then uses a simple call to the DBIC "create" method
102 to add the requested information to the database (with a separate call
103 to "add_to_book_authors" to update the join table). As do virtually
104 all controller methods (at least the ones that directly handle user
105 input), it then sets the template that should handle this request.
106 Also note that we are explicitly setting a "no-cache" "Cache-Control"
108 header to force browsers using the page to get a fresh copy every time.
109 You could even move this to a "auto" method in
110 lib/MyApp/Controller/Root.pm and it would automatically get applied to
111 every page in the whole application via a single line of code (remember
112 from Chapter 3, that every "auto" method gets run in the Controller
113 hierarchy).
114 Include a Template for the 'url_create' Action:
116 Edit root/src/books/create_done.tt2 and then enter:
117 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
119 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
120 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
121 [% USE Dumper(Indent=1) -%]
122 [% # Set the page title. META can 'go back' and set values in templates -%]
124 [% # that have been processed 'before' this template (here it's updating -%]
125 [% # the title in the root/src/wrapper.tt2 wrapper template). Note that -%]
126 [% # META only works on simple/static strings (i.e. there is no variable -%]
127 [% # interpolation -- if you need dynamic/interpolated content in your -%]
128 [% # title, set "$c->stash(title => $something)" in the controller). -%]
129 [% META title = 'Book Created' %]
130 [% # Output information about the record that was added. First title. -%]
132 <p>Added book '[% book.title %]'
133 [% # Then, output the last name of the first author -%]
135 by '[% book.authors.first.last_name %]'
136 [% # Then, output the rating for the book that was added -%]
138 with a rating of [% book.rating %].</p>
139 [% # Provide a link back to the list page. 'c.uri_for' builds -%]
141 [% # a full URI; e.g., 'http://localhost:3000/books/list' -%]
142 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
143 [% # Try out the TT Dumper (for development only!) -%]
145 <pre>
146 Dump of the 'book' variable:
147 [% Dumper.dump(book) %]
148 </pre>
149 The TT "USE" directive allows access to a variety of plugin modules (TT
151 plugins, that is, not Catalyst plugins) to add extra functionality to
152 the base TT capabilities. Here, the plugin allows Data::Dumper "pretty
153 printing" of objects and variables. Other than that, the rest of the
154 code should be familiar from the examples in Chapter 3.
155 Try the 'url_create' Feature
157 Make sure the development server is running with the "-r" restart
158 option:
159 $ DBIC_TRACE=1 script/myapp_server.pl -r
161 Note that new path for "/books/url_create" appears in the startup debug
163 output.
164 Next, use your browser to enter the following URL:
166 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
168 Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
170 'Stevens' with a rating of 5." along with a dump of the new book model
171 object as it was returned by DBIC. You should also see the following
172 DBIC debug messages displayed in the development server log messages if
173 you have DBIC_TRACE set:
174 INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
176 INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6'
177 The "INSERT" statements are obviously adding the book and linking it to
179 the existing record for Richard Stevens. The "SELECT" statement
180 results from DBIC automatically fetching the book for the
181 "Dumper.dump(book)".
182 If you then click the "Return to list" link, you should find that there
184 are now six books shown (if necessary, Shift+Reload or Ctrl+Reload your
185 browser at the "/books/list" page). You should now see the six DBIC
186 debug messages similar to the following (where N=1-6):
187 SELECT author.id, author.first_name, author.last_name
189 FROM book_author me JOIN author author
190 ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N'
191
193 Although the example above uses the same "Local" action type for the
194 method that we saw in the previous chapter of the tutorial, there is an
195 alternate approach that allows us to be more specific while also paving
196 the way for more advanced capabilities. Change the method declaration
197 for "url_create" in lib/MyApp/Controller/Books.pm you entered above to
198 match the following:
199 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
201 # In addition to self & context, get the title, rating, &
202 # author_id args from the URL. Note that Catalyst automatically
203 # puts the first 3 arguments worth of extra information after the
204 # "/<controller_name>/<action_name/" into @_ because we specified
205 # "Args(3)". The args are separated by the '/' char on the URL.
206 my ($self, $c, $title, $rating, $author_id) = @_;
207 ...
209 This converts the method to take advantage of the Chained
211 action/dispatch type. Chaining lets you have a single URL automatically
212 dispatch to several controller methods, each of which can have precise
213 control over the number of arguments that it will receive. A chain can
214 essentially be thought of having three parts -- a beginning, a middle,
215 and an end. The bullets below summarize the key points behind each of
216 these parts of a chain:
217 · Beginning
219 · Use "":Chained('/')"" to start a chain
221 · Get arguments through "CaptureArgs()"
223 · Specify the path to match with "PathPart()"
225 · Middle
227 · Link to previous part of the chain with ":Chained('_name_')"
229 · Get arguments through "CaptureArgs()"
231 · Specify the path to match with "PathPart()"
233 · End
235 · Link to previous part of the chain with ":Chained('_name_')"
237 · Do NOT get arguments through ""CaptureArgs()"," use ""Args()""
239 instead to end a chain
240 · Specify the path to match with "PathPart()"
242 In our "url_create" method above, we have combined all three parts into
244 a single method: ":Chained('/')" to start the chain,
245 ":PathPart('books/url_create')" to specify the base URL to match, and
246 :Args(3) to capture exactly three arguments and to end the chain.
247 As we will see shortly, a chain can consist of as many "links" as you
249 wish, with each part capturing some arguments and doing some work along
250 the way. We will continue to use the Chained action type in this
251 chapter of the tutorial and explore slightly more advanced capabilities
252 with the base method and delete feature below. But Chained dispatch is
253 capable of far more. For additional information, see "Action types" in
254 Catalyst::Manual::Intro, Catalyst::DispatchType::Chained, and the 2006
255 Advent calendar entry on the subject:
256 <http://www.catalystframework.org/calendar/2006/10>.
257 Try the Chained Action
259 If you look back at the development server startup logs from your
260 initial version of the "url_create" method (the one using the ":Local"
261 attribute), you will notice that it produced output similar to the
262 following:
263 [debug] Loaded Path actions:
265 .-------------------------------------+--------------------------------------.
266 | Path | Private |
267 +-------------------------------------+--------------------------------------+
268 | / | /default |
269 | / | /index |
270 | /books | /books/index |
271 | /books/list | /books/list |
272 | /books/url_create | /books/url_create |
273 '-------------------------------------+--------------------------------------'
274 When the development server restarts after our conversion to Chained
276 dispatch, the debug output should change to something along the lines
277 of the following:
278 [debug] Loaded Path actions:
280 .-------------------------------------+--------------------------------------.
281 | Path | Private |
282 +-------------------------------------+--------------------------------------+
283 | / | /default |
284 | / | /index |
285 | /books | /books/index |
286 | /books/list | /books/list |
287 '-------------------------------------+--------------------------------------'
288 [debug] Loaded Chained actions:
290 .-------------------------------------+--------------------------------------.
291 | Path Spec | Private |
292 +-------------------------------------+--------------------------------------+
293 | /books/url_create/*/*/* | /books/url_create |
294 '-------------------------------------+--------------------------------------'
295 "url_create" has disappeared from the "Loaded Path actions" section but
297 it now shows up under the newly created "Loaded Chained actions"
298 section. And the "/*/*/*" portion clearly shows our requirement for
299 three arguments.
300 As with our non-chained version of "url_create", use your browser to
302 enter the following URL:
303 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
305 You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
307 'Stevens' with a rating of 5." along with a dump of the new book model
308 object. Click the "Return to list" link, and you should find that
309 there are now seven books shown (two copies of
310 TCPIP_Illustrated_Vol-2).
311 Refactor to Use a 'base' Method to Start the Chains
313 Let's make a quick update to our initial Chained action to show a
314 little more of the power of chaining. First, open
315 lib/MyApp/Controller/Books.pm in your editor and add the following
316 method:
317 =head2 base
319 Can place common logic to start chained dispatch here
321 =cut
323 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
325 my ($self, $c) = @_;
326 # Store the ResultSet in stash so it's available for other methods
328 $c->stash(resultset => $c->model('DB::Book'));
329 # Print a message to the debug log
331 $c->log->debug('*** INSIDE BASE METHOD ***');
332 }
333 Here we print a log message and store the DBIC ResultSet in
335 "$c->stash->{resultset}" so that it's automatically available for other
336 actions that chain off "base". If your controller always needs a book
337 ID as its first argument, you could have the base method capture that
338 argument (with :CaptureArgs(1)) and use it to pull the book object with
339 "->find($id)" and leave it in the stash for later parts of your chains
340 to then act upon. Because we have several actions that don't need to
341 retrieve a book (such as the "url_create" we are working with now), we
342 will instead add that functionality to a common "object" action
343 shortly.
344 As for "url_create", let's modify it to first dispatch to "base". Open
346 up lib/MyApp/Controller/Books.pm and edit the declaration for
347 "url_create" to match the following:
348 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
350 Once you save lib/MyApp/Controller/Books.pm, notice that the
352 development server will restart and our "Loaded Chained actions"
353 section will changed slightly:
354 [debug] Loaded Chained actions:
356 .-------------------------------------+--------------------------------------.
357 | Path Spec | Private |
358 +-------------------------------------+--------------------------------------+
359 | /books/url_create/*/*/* | /books/base (0) |
360 | | => /books/url_create |
361 '-------------------------------------+--------------------------------------'
362 The "Path Spec" is the same, but now it maps to two Private actions as
364 we would expect. The "base" method is being triggered by the "/books"
365 part of the URL. However, the processing then continues to the
366 "url_create" method because this method "chained" off "base" and
367 specified ":PathPart('url_create')" (note that we could have omitted
368 the "PathPart" here because it matches the name of the method, but we
369 will include it to make the logic as explicit as possible).
370 Once again, enter the following URL into your browser:
372 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
374 The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
376 rating of 5." message and a dump of the new book object should appear.
377 Also notice the extra "INSIDE BASE METHOD" debug message in the
378 development server output from the "base" method. Click the "Return to
379 list" link, and you should find that there are now eight books shown.
380 (You may have a larger number of books if you repeated any of the
381 "create" actions more than once. Don't worry about it as long as the
382 number of books is appropriate for the number of times you added new
383 books... there should be the original five books added via myapp01.sql
384 plus one additional book for each time you ran one of the url_create
385 variations above.)
386
388 Although the "url_create" action in the previous step does begin to
389 reveal the power and flexibility of both Catalyst and DBIC, it's
390 obviously not a very realistic example of how users should be expected
391 to enter data. This section begins to address that concern (but just
392 barely, see Chapter 9 for better options for handling web-based forms).
393 Add Method to Display The Form
395 Edit lib/MyApp/Controller/Books.pm and add the following method:
396 =head2 form_create
398 Display form to collect information for book to create
400 =cut
402 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
404 my ($self, $c) = @_;
405 # Set the TT template to use
407 $c->stash(template => 'books/form_create.tt2');
408 }
409 This action simply invokes a view containing a form to create a book.
411 Add a Template for the Form
413 Open root/src/books/form_create.tt2 in your editor and enter:
414 [% META title = 'Manual Form Book Create' -%]
416 <form method="post" action="[% c.uri_for('form_create_do') %]">
418 <table>
419 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
420 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
421 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
422 </table>
423 <input type="submit" name="Submit" value="Submit">
424 </form>
425 Note that we have specified the target of the form data as
427 "form_create_do", the method created in the section that follows.
428 Add a Method to Process Form Values and Update Database
430 Edit lib/MyApp/Controller/Books.pm and add the following method to save
431 the form information to the database:
432 =head2 form_create_do
434 Take information from form and add to database
436 =cut
438 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
440 my ($self, $c) = @_;
441 # Retrieve the values from the form
443 my $title = $c->request->params->{title} || 'N/A';
444 my $rating = $c->request->params->{rating} || 'N/A';
445 my $author_id = $c->request->params->{author_id} || '1';
446 # Create the book
448 my $book = $c->model('DB::Book')->create({
449 title => $title,
450 rating => $rating,
451 });
452 # Handle relationship with author
453 $book->add_to_book_authors({author_id => $author_id});
454 # Note: Above is a shortcut for this:
455 # $book->create_related('book_authors', {author_id => $author_id});
456 # Store new model object in stash and set template
458 $c->stash(book => $book,
459 template => 'books/create_done.tt2');
460 }
461 Test Out The Form
463 Notice that the server startup log reflects the two new chained methods
464 that we added:
465 [debug] Loaded Chained actions:
467 .-------------------------------------+--------------------------------------.
468 | Path Spec | Private |
469 +-------------------------------------+--------------------------------------+
470 | /books/form_create | /books/base (0) |
471 | | => /books/form_create |
472 | /books/form_create_do | /books/base (0) |
473 | | => /books/form_create_do |
474 | /books/url_create/*/*/* | /books/base (0) |
475 | | => /books/url_create |
476 '-------------------------------------+--------------------------------------'
477 Point your browser to <http://localhost:3000/books/form_create> and
479 enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
480 author ID of 4. You should then see the output of the same
481 create_done.tt2 template seen in earlier examples. Finally, click
482 "Return to list" to view the full list of books.
483 Note: Having the user enter the primary key ID for the author is
485 obviously crude; we will address this concern with a drop-down list and
486 add validation to our forms in Chapter 9.
487
489 Turning our attention to the Delete portion of CRUD, this section
490 illustrates some basic techniques that can be used to remove
491 information from the database.
492 Include a Delete Link in the List
494 Edit root/src/books/list.tt2 and update it to match the following (two
495 sections have changed: 1) the additional '<th>Links</th>' table header,
496 and 2) the five lines for the Delete link near the bottom):
497 [% # This is a TT comment. -%]
499 [%- # Provide a title -%]
501 [% META title = 'Book List' -%]
502 [% # Note That the '-' at the beginning or end of TT code -%]
504 [% # "chomps" the whitespace/newline at that end of the -%]
505 [% # output (use View Source in browser to see the effect) -%]
506 [% # Some basic HTML with a loop to display books -%]
508 <table>
509 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
510 [% # Display each book in a table row %]
511 [% FOREACH book IN books -%]
512 <tr>
513 <td>[% book.title %]</td>
514 <td>[% book.rating %]</td>
515 <td>
516 [% # NOTE: See Chapter 4 for a better way to do this! -%]
517 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
518 [% # loop in 'side effect notation' to load just the last names of the -%]
519 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
520 [% # a value, so nothing will be printed here. But, if you have something -%]
521 [% # in TT that does return a value and you don't want it printed, you -%]
522 [% # 1) assign it to a bogus value, or -%]
523 [% # 2) use the CALL keyword to call it and discard the return value. -%]
524 [% tt_authors = [ ];
525 tt_authors.push(author.last_name) FOREACH author = book.authors %]
526 [% # Now use a TT 'virtual method' to display the author count in parens -%]
527 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
528 ([% tt_authors.size | html %])
529 [% # Use another TT vmethod to join & print the names & comma separators -%]
530 [% tt_authors.join(', ') | html %]
531 </td>
532 <td>
533 [% # Add a link to delete a book %]
534 <a href="[%
535 c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
536 </td>
537 </tr>
538 [% END -%]
539 </table>
540 The additional code is obviously designed to add a new column to the
542 right side of the table with a "Delete" "button" (for simplicity, links
543 will be used instead of full HTML buttons; but, in practice, anything
544 that modifies data should be handled with a form sending a POST
545 request).
546 Also notice that we are using a more advanced form of "uri_for" than we
548 have seen before. Here we use "$c->controller->action_for" to
549 automatically generate a URI appropriate for that action based on the
550 method we want to link to while inserting the "book.id" value into the
551 appropriate place. Now, if you ever change ":PathPart('delete')" in
552 your controller method to something like ":PathPart('kill')", then your
553 links will automatically update without any changes to your .tt2
554 template file. As long as the name of your method does not change
555 (here, "delete"), then your links will still be correct. There are a
556 few shortcuts and options when using "action_for()":
557 · If you are referring to a method in the current controller, you can
559 use "$self->action_for('_method_name_')".
560 · If you are referring to a method in a different controller, you
562 need to include that controller's name as an argument to
563 "controller()", as in
564 "$c->controller('_controller_name_')->action_for('_method_name_')".
565 Note: In practice you should never use a GET request to delete a record
567 -- always use POST for actions that will modify data. We are doing it
568 here for illustrative and simplicity purposes only.
569 Add a Common Method to Retrieve a Book for the Chain
571 As mentioned earlier, since we have a mixture of actions that operate
572 on a single book ID and others that do not, we should not have "base"
573 capture the book ID, find the corresponding book in the database and
574 save it in the stash for later links in the chain. However, just
575 because that logic does not belong in "base" doesn't mean that we can't
576 create another location to centralize the book lookup code. In our
577 case, we will create a method called "object" that will store the
578 specific book in the stash. Chains that always operate on a single
579 existing book can chain off this method, but methods such as
580 "url_create" that don't operate on an existing book can chain directly
581 off base.
582 To add the "object" method, edit lib/MyApp/Controller/Books.pm and add
584 the following code:
585 =head2 object
587 Fetch the specified book object based on the book ID and store
589 it in the stash
590 =cut
592 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
594 # $id = primary key of book to delete
595 my ($self, $c, $id) = @_;
596 # Find the book object and store it in the stash
598 $c->stash(object => $c->stash->{resultset}->find($id));
599 # Make sure the lookup was successful. You would probably
601 # want to do something like this in a real app:
602 # $c->detach('/error_404') if !$c->stash->{object};
603 die "Book $id not found!" if !$c->stash->{object};
604 # Print a message to the debug log
606 $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***");
607 }
608 Now, any other method that chains off "object" will automatically have
610 the appropriate book waiting for it in "$c->stash->{object}".
611 Add a Delete Action to the Controller
613 Open lib/MyApp/Controller/Books.pm in your editor and add the following
614 method:
615 =head2 delete
617 Delete a book
619 =cut
621 sub delete :Chained('object') :PathPart('delete') :Args(0) {
623 my ($self, $c) = @_;
624 # Use the book object saved by 'object' and delete it along
626 # with related 'book_author' entries
627 $c->stash->{object}->delete;
628 # Set a status message to be displayed at the top of the view
630 $c->stash->{status_msg} = "Book deleted.";
631 # Forward to the list action/method in this controller
633 $c->forward('list');
634 }
635 This method first deletes the book object saved by the "object" method.
637 However, it also removes the corresponding entry from the "book_author"
638 table with a cascading delete.
639 Then, rather than forwarding to a "delete done" page as we did with the
641 earlier create example, it simply sets the "status_msg" to display a
642 notification to the user as the normal list view is rendered.
643 The "delete" action uses the context "forward" method to return the
645 user to the book list. The "detach" method could have also been used.
646 Whereas "forward" returns to the original action once it is completed,
647 "detach" does not return. Other than that, the two are equivalent.
648 Try the Delete Feature
650 Once you save the Books controller, the server should automatically
651 restart. The "delete" method should now appear in the "Loaded Chained
652 actions" section of the startup debug output:
653 [debug] Loaded Chained actions:
655 .-------------------------------------+--------------------------------------.
656 | Path Spec | Private |
657 +-------------------------------------+--------------------------------------+
658 | /books/id/*/delete | /books/base (0) |
659 | | -> /books/object (1) |
660 | | => /books/delete |
661 | /books/form_create | /books/base (0) |
662 | | => /books/form_create |
663 | /books/form_create_do | /books/base (0) |
664 | | => /books/form_create_do |
665 | /books/url_create/*/*/* | /books/base (0) |
666 | | => /books/url_create |
667 '-------------------------------------+--------------------------------------'
668 Then point your browser to <http://localhost:3000/books/list> and click
670 the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
671 "Book deleted" status message should display at the top of the page,
672 along with a list of the eight remaining books. You will also see the
673 cascading delete operation via the DBIC_TRACE output:
674 SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6'
676 DELETE FROM book WHERE ( id = ? ): '6'
677 If you get the error "file error - books/delete.tt2: not found" then
679 you probably forgot to uncomment the template line in "sub list" at the
680 end of chapter 3.
681 Fixing a Dangerous URL
683 Note the URL in your browser once you have performed the deletion in
684 the prior step -- it is still referencing the delete action:
685 http://localhost:3000/books/id/6/delete
687 What if the user were to press reload with this URL still active? In
689 this case the redundant delete is harmless (although it does generate
690 an exception screen, it doesn't perform any undesirable actions on the
691 application or database), but in other cases this could clearly lead to
692 trouble.
693 We can improve the logic by converting to a redirect. Unlike
695 "$c->forward('list'))" or "$c->detach('list'))" that perform a server-
696 side alteration in the flow of processing, a redirect is a client-side
697 mechanism that causes the browser to issue an entirely new request. As
698 a result, the URL in the browser is updated to match the destination of
699 the redirection URL.
700 To convert the forward used in the previous section to a redirect, open
702 lib/MyApp/Controller/Books.pm and edit the existing "sub delete" method
703 to match:
704 =head2 delete
706 Delete a book
708 =cut
710 sub delete :Chained('object') :PathPart('delete') :Args(0) {
712 my ($self, $c) = @_;
713 # Use the book object saved by 'object' and delete it along
715 # with related 'book_author' entries
716 $c->stash->{object}->delete;
717 # Set a status message to be displayed at the top of the view
719 $c->stash->{status_msg} = "Book deleted.";
720 # Redirect the user back to the list page. Note the use
722 # of $self->action_for as earlier in this section (BasicCRUD)
723 $c->response->redirect($c->uri_for($self->action_for('list')));
724 }
725 Try the Delete and Redirect Logic
727 Point your browser to <http://localhost:3000/books/list> (don't just
728 hit "Refresh" in your browser since we left the URL in an invalid state
729 in the previous section!) and delete the first copy of the remaining
730 two "TCPIP_Illustrated_Vol-2" books. The URL in your browser should
731 return to the <http://localhost:3000/books/list> URL, so that is an
732 improvement, but notice that no green "Book deleted" status message is
733 displayed. Because the stash is reset on every request (and a redirect
734 involves a second request), the "status_msg" is cleared before it can
735 be displayed.
736 Using 'uri_for' to Pass Query Parameters
738 There are several ways to pass information across a redirect. One
739 option is to use the "flash" technique that we will see in Chapter 5 of
740 this tutorial; however, here we will pass the information via query
741 parameters on the redirect itself. Open lib/MyApp/Controller/Books.pm
742 and update the existing "sub delete" method to match the following:
743 =head2 delete
745 Delete a book
747 =cut
749 sub delete :Chained('object') :PathPart('delete') :Args(0) {
751 my ($self, $c) = @_;
752 # Use the book object saved by 'object' and delete it along
754 # with related 'book_author' entries
755 $c->stash->{object}->delete;
756 # Redirect the user back to the list page with status msg as an arg
758 $c->response->redirect($c->uri_for($self->action_for('list'),
759 {status_msg => "Book deleted."}));
760 }
761 This modification simply leverages the ability of "uri_for" to include
763 an arbitrary number of name/value pairs in a hash reference. Next, we
764 need to update root/src/wrapper.tt2 to handle "status_msg" as a query
765 parameter:
766 ...
768 <div id="content">
769 [%# Status and error messages %]
770 <span class="message">[%
771 status_msg || c.request.params.status_msg | html %]</span>
772 <span class="error">[% error_msg %]</span>
773 [%# This is where TT will stick all of your template's contents. -%]
774 [% content %]
775 </div><!-- end content -->
776 ...
777 Although the sample above only shows the "content" div, leave the rest
779 of the file intact -- the only change we made to the wrapper.tt2 was to
780 add ""|| c.request.params.status_msg"" to the "<span class="message">"
781 line. Note that we definitely want the ""| html"" TT filter here since
782 it would be easy for users to modify the message on the URL and
783 possibly inject harmful code into the application if we left that off.
784 Try the Delete and Redirect With Query Param Logic
786 Point your browser to <http://localhost:3000/books/list> (you should
787 now be able to safely hit "refresh" in your browser). Then delete the
788 remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted"
789 status message should return. But notice that you can now hit the
790 "Reload" button in your browser and it just redisplays the book list
791 (and it correctly shows it without the "Book deleted" message on
792 redisplay).
793 NOTE: Be sure to check out Authentication where we use an improved
795 technique that is better suited to your real world applications.
796
798 In this section we will explore some additional capabilities offered by
799 DBIx::Class. Although these features have relatively little to do with
800 Catalyst per se, you will almost certainly want to take advantage of
801 them in your applications.
802 Add Datetime Columns to Our Existing Books Table
804 Let's add two columns to our existing "books" table to track when each
805 book was added and when each book is updated:
806 $ sqlite3 myapp.db
808 sqlite> ALTER TABLE book ADD created TIMESTAMP;
809 sqlite> ALTER TABLE book ADD updated TIMESTAMP;
810 sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
811 sqlite> SELECT * FROM book;
812 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
813 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
814 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
815 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
816 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
817 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
818 sqlite> .quit
819 $
820 Here are the commands without the surrounding sqlite3 prompt and output
822 in case you want to cut and paste them as a single block (but still
823 start sqlite3 before you paste these in):
824 ALTER TABLE book ADD created TIMESTAMP;
826 ALTER TABLE book ADD updated TIMESTAMP;
827 UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
828 SELECT * FROM book;
829 This will modify the "books" table to include the two new fields and
831 populate those fields with the current time.
832 Update DBIx::Class to Automatically Handle the Datetime Columns
834 Next, we should re-run the DBIC helper to update the Result Classes
835 with the new fields:
836 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
838 create=static components=TimeStamp dbi:SQLite:myapp.db \
839 on_connect_do="PRAGMA foreign_keys = ON"
840 exists "/home/catalyst/dev/MyApp/script/../lib/MyApp/Model"
841 exists "/home/catalyst/dev/MyApp/script/../t"
842 Dumping manual schema for MyApp::Schema to directory /home/catalyst/dev/MyApp/script/../lib ...
843 Schema dump completed.
844 exists "/home/catalyst/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
845 Notice that we modified our use of the helper slightly: we told it to
847 include the DBIx::Class::TimeStamp in the "load_components" line of the
848 Result Classes.
849 If you open lib/MyApp/Schema/Result/Book.pm in your editor you should
851 see that the "created" and "updated" fields are now included in the
852 call to "add_columns()". However, also notice that the "many_to_many"
853 relationships we manually added below the ""# DO NOT MODIFY..."" line
854 were automatically preserved.
855 While we lib/MyApp/Schema/Result/Book.pm open, let's update it with
857 some additional information to have DBIC automatically handle the
858 updating of these two fields for us. Insert the following code at the
859 bottom of the file (it must be below the ""# DO NOT MODIFY..."" line
860 and above the "1;" on the last line):
861 #
863 # Enable automatic date handling
864 #
865 __PACKAGE__->add_columns(
866 "created",
867 { data_type => 'timestamp', set_on_create => 1 },
868 "updated",
869 { data_type => 'timestamp', set_on_create => 1, set_on_update => 1 },
870 );
871 This will override the definition for these fields that Schema::Loader
873 placed at the top of the file. The "set_on_create" and "set_on_update"
874 options will cause DBIx::Class to automatically update the timestamps
875 in these columns whenever a row is created or modified.
876 Note that adding the lines above will cause the development server to
878 automatically restart if you are running it with the "-r" option. In
879 other words, the development server is smart enough to restart not only
880 for code under the MyApp/Controller/, MyApp/Model/, and MyApp/View/
881 directories, but also under other directions such as our "external DBIC
882 model" in MyApp/Schema/. However, also note that it's smart enough to
883 not restart when you edit your ".tt2" files under root/.
884 Then enter the following URL into your web browser:
886 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
888 You should get the same "Book Created" screen we saw earlier. However,
890 if you now use the sqlite3 command-line tool to dump the "books" table,
891 you will see that the new book we added has an appropriate date and
892 time entered for it (see the last line in the listing below):
893 $ sqlite3 myapp.db "select * from book"
895 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
896 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
897 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
898 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
899 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
900 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
901 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42
902 Notice in the debug log that the SQL DBIC generated has changed to
904 incorporate the datetime logic:
905 INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
907 '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42'
908 INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10'
909 Create a ResultSet Class
911 An often overlooked but extremely powerful features of DBIC is that it
912 allows you to supply your own subclasses of DBIx::Class::ResultSet.
913 This can be used to pull complex and unsightly "query code" out of your
914 controllers and encapsulate it in a method of your ResultSet Class.
915 These "canned queries" in your ResultSet Class can then be invoked via
916 a single call, resulting in much cleaner and easier to read controller
917 code (or View code, if that's where you want to call it).
918 To illustrate the concept with a fairly simple example, let's create a
920 method that returns books added in the last 10 minutes. Start by
921 making a directory where DBIx::Class will look for our ResultSet Class:
922 $ mkdir lib/MyApp/Schema/ResultSet
924 Then open lib/MyApp/Schema/ResultSet/Book.pm and enter the following:
926 package MyApp::Schema::ResultSet::Book;
928 use strict;
930 use warnings;
931 use base 'DBIx::Class::ResultSet';
932 =head2 created_after
934 A predefined search for recently added books
936 =cut
938 sub created_after {
940 my ($self, $datetime) = @_;
941 my $date_str = $self->result_source->schema->storage
943 ->datetime_parser->format_datetime($datetime);
944 return $self->search({
946 created => { '>' => $date_str }
947 });
948 }
949 1;
951 Then add the following method to the lib/MyApp/Controller/Books.pm:
953 =head2 list_recent
955 List recently created books
957 =cut
959 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
961 my ($self, $c, $mins) = @_;
962 # Retrieve all of the book records as book model objects and store in the
964 # stash where they can be accessed by the TT template, but only
965 # retrieve books created within the last $min number of minutes
966 $c->stash(books => [$c->model('DB::Book')
967 ->created_after(DateTime->now->subtract(minutes => $mins))]);
968 # Set the TT template to use. You will almost always want to do this
970 # in your action methods (action methods respond to user input in
971 # your controllers).
972 $c->stash(template => 'books/list.tt2');
973 }
974 Now try different values for the "minutes" argument (the final number
976 value) using the URL "http://localhost:3000/books/list_recent/_#_" in
977 your browser. For example, this would list all books added in the last
978 fifteen minutes:
979 http://localhost:3000/books/list_recent/15
981 Depending on how recently you added books, you might want to try a
983 higher or lower value for the minutes.
984 Chaining ResultSets
986 One of the most helpful and powerful features in DBIx::Class is that it
987 allows you to "chain together" a series of queries (note that this has
988 nothing to do with the "Chained Dispatch" for Catalyst that we were
989 discussing earlier). Because each ResultSet method returns another
990 ResultSet, you can take an initial query and immediately feed that into
991 a second query (and so on for as many queries you need). Note that no
992 matter how many ResultSets you chain together, the database itself will
993 not be hit until you use a method that attempts to access the data.
994 And, because this technique carries over to the ResultSet Class feature
995 we implemented in the previous section for our "canned search", we can
996 combine the two capabilities. For example, let's add an action to our
997 "Books" controller that lists books that are both recent and have "TCP"
998 in the title. Open up lib/MyApp/Controller/Books.pm and add the
999 following method:
1000 =head2 list_recent_tcp
1002 List recently created books
1004 =cut
1006 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1008 my ($self, $c, $mins) = @_;
1009 # Retrieve all of the book records as book model objects and store in the
1011 # stash where they can be accessed by the TT template, but only
1012 # retrieve books created within the last $min number of minutes
1013 # AND that have 'TCP' in the title
1014 $c->stash(books => [
1015 $c->model('DB::Book')
1016 ->created_after(DateTime->now->subtract(minutes => $mins))
1017 ->search({title => {'like', '%TCP%'}})
1018 ]);
1019 # Set the TT template to use. You will almost always want to do this
1021 # in your action methods (action methods respond to user input in
1022 # your controllers).
1023 $c->stash(template => 'books/list.tt2');
1024 }
1025 To try this out, enter the following URL into your browser:
1027 http://localhost:3000/books/list_recent_tcp/100
1029 And you should get a list of books added in the last 100 minutes that
1031 contain the string "TCP" in the title. However, if you look at all
1032 books within the last 100 minutes, you should get a longer list (again,
1033 you might have to adjust the number of minutes depending on how
1034 recently you added books to your database):
1035 http://localhost:3000/books/list_recent/100
1037 Take a look at the DBIC_TRACE output in the development server log for
1039 the first URL and you should see something similar to the following:
1040 SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me
1042 WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32'
1043 However, let's not pollute our controller code with this raw "TCP"
1045 query -- it would be cleaner to encapsulate that code in a method on
1046 our ResultSet Class. To do this, open
1047 lib/MyApp/Schema/ResultSet/Book.pm and add the following method:
1048 =head2 title_like
1050 A predefined search for books with a 'LIKE' search in the string
1052 =cut
1054 sub title_like {
1056 my ($self, $title_str) = @_;
1057 return $self->search({
1059 title => { 'like' => "%$title_str%" }
1060 });
1061 }
1062 We defined the search string as $title_str to make the method more
1064 flexible. Now update the "list_recent_tcp" method in
1065 lib/MyApp/Controller/Books.pm to match the following (we have replaced
1066 the "->search" line with the "->title_like" line shown here -- the rest
1067 of the method should be the same):
1068 =head2 list_recent_tcp
1070 List recently created books
1072 =cut
1074 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1076 my ($self, $c, $mins) = @_;
1077 # Retrieve all of the book records as book model objects and store in the
1079 # stash where they can be accessed by the TT template, but only
1080 # retrieve books created within the last $min number of minutes
1081 # AND that have 'TCP' in the title
1082 $c->stash(books => [
1083 $c->model('DB::Book')
1084 ->created_after(DateTime->now->subtract(minutes => $mins))
1085 ->title_like('TCP')
1086 ]);
1087 # Set the TT template to use. You will almost always want to do this
1089 # in your action methods (action methods respond to user input in
1090 # your controllers).
1091 $c->stash(template => 'books/list.tt2');
1092 }
1093 Try out the "list_recent_tcp" and "list_recent" URLs as we did above.
1095 They should work just the same, but our code is obviously cleaner and
1096 more modular, while also being more flexible at the same time.
1097 Adding Methods to Result Classes
1099 In the previous two sections we saw a good example of how we could use
1100 DBIx::Class ResultSet Classes to clean up our code for an entire query
1101 (for example, our "canned searches" that filtered the entire query).
1102 We can do a similar improvement when working with individual rows as
1103 well. Whereas the ResultSet construct is used in DBIC to correspond to
1104 an entire query, the Result Class construct is used to represent a row.
1105 Therefore, we can add row-specific "helper methods" to our Result
1106 Classes stored in lib/MyApp/Schema/Result/. For example, open
1107 lib/MyApp/Schema/Result/Author.pm and add the following method (as
1108 always, it must be above the closing ""1;""):
1109 #
1111 # Row-level helper methods
1112 #
1113 sub full_name {
1114 my ($self) = @_;
1115 return $self->first_name . ' ' . $self->last_name;
1117 }
1118 This will allow us to conveniently retrieve both the first and last
1120 name for an author in one shot. Now open root/src/books/list.tt2 and
1121 change the definition of "tt_authors" from this:
1122 ...
1124 [% tt_authors = [ ];
1125 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1126 ...
1127 to:
1129 ...
1131 [% tt_authors = [ ];
1132 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1133 ...
1134 (Only "author.last_name" was changed to "author.full_name" -- the rest
1136 of the file should remain the same.)
1137 Now go to the standard book list URL:
1139 http://localhost:3000/books/list
1141 The "Author(s)" column will now contain both the first and last name.
1143 And, because the concatenation logic was encapsulated inside our Result
1144 Class, it keeps the code inside our TT template nice and clean
1145 (remember, we want the templates to be as close to pure HTML markup as
1146 possible). Obviously, this capability becomes even more useful as you
1147 use it to remove even more complicated row-specific logic from your
1148 templates!
1149 Moving Complicated View Code to the Model
1151 The previous section illustrated how we could use a Result Class method
1152 to print the full names of the authors without adding any extra code to
1153 our view, but it still left us with a fairly ugly mess (see
1154 root/src/books/list.tt2):
1155 ...
1157 <td>
1158 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1159 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1160 [% # loop in 'side effect notation' to load just the last names of the -%]
1161 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1162 [% # a value, so nothing will be printed here. But, if you have something -%]
1163 [% # in TT that does return a method and you don't want it printed, you -%]
1164 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1165 [% # call it and discard the return value. -%]
1166 [% tt_authors = [ ];
1167 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1168 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1169 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1170 ([% tt_authors.size | html %])
1171 [% # Use another TT vmethod to join & print the names & comma separators -%]
1172 [% tt_authors.join(', ') | html %]
1173 </td>
1174 ...
1175 Let's combine some of the techniques used earlier in this section to
1177 clean this up. First, let's add a method to our Book Result Class to
1178 return the number of authors for a book. Open
1179 lib/MyApp/Schema/Result/Book.pm and add the following method:
1180 =head2 author_count
1182 Return the number of authors for the current book
1184 =cut
1186 sub author_count {
1188 my ($self) = @_;
1189 # Use the 'many_to_many' relationship to fetch all of the authors for the current
1191 # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
1192 return $self->authors->count;
1193 }
1194 Next, let's add a method to return a list of authors for a book to the
1196 same lib/MyApp/Schema/Result/Book.pm file:
1197 =head2 author_list
1199 Return a comma-separated list of authors for the current book
1201 =cut
1203 sub author_list {
1205 my ($self) = @_;
1206 # Loop through all authors for the current book, calling all the 'full_name'
1208 # Result Class method for each
1209 my @names;
1210 foreach my $author ($self->authors) {
1211 push(@names, $author->full_name);
1212 }
1213 return join(', ', @names);
1215 }
1216 This method loops through each author, using the "full_name" Result
1218 Class method we added to lib/MyApp/Schema/Result/Author.pm in the prior
1219 section.
1220 Using these two methods, we can simplify our TT code. Open
1222 root/src/books/list.tt2 and update the "Author(s)" table cell to match
1223 the following:
1224 ...
1226 <td>
1227 [% # Print count and author list using Result Class methods -%]
1228 ([% book.author_count | html %]) [% book.author_list | html %]
1229 </td>
1230 ...
1231 Although most of the code we removed comprised comments, the overall
1233 effect is dramatic... because our view code is so simple, we don't need
1234 huge comments to clue people in to the gist of our code. The view code
1235 is now self-documenting and readable enough that you could probably get
1236 by with no comments at all. All of the "complex" work is being done in
1237 our Result Class methods (and, because we have broken the code into
1238 nice, modular chunks, the Result Class code is hardly something you
1239 would call complex).
1240 As we saw in this section, always strive to keep your view AND
1242 controller code as simple as possible by pulling code out into your
1243 model objects. Because DBIx::Class can be easily extended in so many
1244 ways, it's an excellent to way accomplish this objective. It will make
1245 your code cleaner, easier to write, less error-prone, and easier to
1246 debug and maintain.
1247 Before you conclude this section, hit Refresh in your browser... the
1249 output should be the same even though the backend code has been trimmed
1250 down.
1251 You can jump to the next chapter of the tutorial here: Authentication
1253
1255 Kennedy Clark, "hkclark@gmail.com"
1256 Feel free to contact the author for any errors or suggestions, but the
1258 best way to report issues is via the CPAN RT Bug system at
1259 <https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
1260 Copyright 2006-2011, Kennedy Clark, under the Creative Commons
1262 Attribution Share-Alike License Version 3.0
1263 (<https://creativecommons.org/licenses/by-sa/3.0/us/>).
1264perl v5.30.1 20C2a0t-a0l1y-s2t9::Manual::Tutorial::04_BasicCRUD(3)