1Mojo::Exception(3) User Contributed Perl Documentation Mojo::Exception(3)
2
6 Mojo::Exception - Exception base class
7
9 # Create exception classes
10 package MyApp::X::Foo {
11 use Mojo::Base 'Mojo::Exception';
12 }
13 package MyApp::X::Bar {
14 use Mojo::Base 'Mojo::Exception';
15 }
16 # Throw exceptions and handle them gracefully
18 use Mojo::Exception 'check';
19 eval {
20 MyApp::X::Foo->throw('Something went wrong!');
21 };
22 check(
23 'MyApp::X::Foo' => sub { say "Foo: $_" },
24 'MyApp::X::Bar' => sub { say "Bar: $_" }
25 );
26 # Generate exception classes on demand
28 use Mojo::Exception qw(check raise);
29 eval {
30 raise 'MyApp::X::Name', 'The name Minion is already taken';
31 };
32 check(
33 'MyApp::X::Name' => sub { say "Name error: $_" },
34 default => sub { say "Error: $_" }
35 );
36
38 Mojo::Exception is a container for exceptions with context information.
39
41 Mojo::Exception implements the following functions, which can be
42 imported individually.
43 check
45 my $bool = check 'MyApp::X::Foo' => sub {...};
46 my $bool = check $err, 'MyApp::X::Foo' => sub {...};
47 Process exceptions by dispatching them to handlers with one or more
49 matching conditions. Exceptions that could not be handled will be
50 rethrown automatically. By default $@ will be used as exception
51 source, so "check" needs to be called right after "eval". Note that
52 this function is EXPERIMENTAL and might change without warning!
53 # Handle various types of exceptions
55 eval {
56 dangerous_code();
57 };
58 check(
59 'MyApp::X::Foo' => sub { say "Foo: $_" },
60 qr/^Could not open/ => sub { say "Open error: $_" },
61 default => sub { say "Something went wrong: $_" },
62 finally => sub { say 'Dangerous code is done' }
63 );
64 Matching conditions can be class names for ISA checks on exception
66 objects, or regular expressions to match string exceptions and
67 stringified exception objects. The matching exception will be the first
68 argument passed to the callback, and is also available as $_.
69 # Catch MyApp::X::Foo object or a specific string exception
71 eval {
72 dangerous_code();
73 };
74 check(
75 'MyApp::X::Foo' => sub { say "Foo: $_" },
76 qr/^Could not open/ => sub { say "Open error: $_" }
77 );
78 An array reference can be used to share the same handler with multiple
80 conditions, of which only one needs to match. And since exception
81 handlers are just callbacks, they can also throw their own exceptions.
82 # Handle MyApp::X::Foo and MyApp::X::Bar the same
84 eval {
85 dangerous_code();
86 };
87 check(
88 ['MyApp::X::Foo', 'MyApp::X::Bar'] => sub { die "Foo/Bar: $_" }
89 );
90 There are currently two keywords you can use to set special handlers.
92 The "default" handler is used when no other handler matched. And the
93 "finally" handler runs always, it does not affect normal handlers and
94 even runs if the exception was rethrown or if there was no exception to
95 be handled at all.
96 # Use "default" to catch everything
98 eval {
99 dangerous_code();
100 };
101 check(
102 default => sub { say "Error: $_" },
103 finally => sub { say 'Dangerous code is done' }
104 );
105 raise
107 raise 'Something went wrong!';
108 raise 'MyApp::X::Foo', 'Something went wrong!';
109 Raise a Mojo::Exception, if the class does not exist yet (classes are
111 checked for a "new" method), one is created as a Mojo::Exception
112 subclass on demand. Note that this function is EXPERIMENTAL and might
113 change without warning!
114
116 Mojo::Exception implements the following attributes.
117 frames
119 my $frames = $e->frames;
120 $e = $e->frames([$frame1, $frame2]);
121 Stack trace if available.
123 # Extract information from the last frame
125 my ($package, $filename, $line, $subroutine, $hasargs, $wantarray, $evaltext,
126 $is_require, $hints, $bitmask, $hinthash) = @{$e->frames->[-1]};
127 line
129 my $line = $e->line;
130 $e = $e->line([3, 'die;']);
131 The line where the exception occurred if available.
133 lines_after
135 my $lines = $e->lines_after;
136 $e = $e->lines_after([[4, 'say $foo;'], [5, 'say $bar;']]);
137 Lines after the line where the exception occurred if available.
139 lines_before
141 my $lines = $e->lines_before;
142 $e = $e->lines_before([[1, 'my $foo = 23;'], [2, 'my $bar = 24;']]);
143 Lines before the line where the exception occurred if available.
145 message
147 my $msg = $e->message;
148 $e = $e->message('Died at test.pl line 3.');
149 Exception message, defaults to "Exception!".
151 verbose
153 my $bool = $e->verbose;
154 $e = $e->verbose($bool);
155 Show more information with "to_string", such as "frames", defaults to
157 the value of the "MOJO_EXCEPTION_VERBOSE" environment variable.
158
160 Mojo::Exception inherits all methods from Mojo::Base and implements the
161 following new ones.
162 inspect
164 $e = $e->inspect;
165 $e = $e->inspect($source1, $source2);
166 Inspect "message", "frames" and optional additional sources to fill
168 "lines_before", "line" and "lines_after" with context information.
169 new
171 my $e = Mojo::Exception->new;
172 my $e = Mojo::Exception->new('Died at test.pl line 3.');
173 Construct a new Mojo::Exception object and assign "message" if
175 necessary.
176 to_string
178 my $str = $e->to_string;
179 Render exception. Note that the output format may change as more
181 features are added, only the error message at the beginning is
182 guaranteed not to be modified to allow regex matching.
183 throw
185 Mojo::Exception->throw('Something went wrong!');
186 Throw exception from the current execution context.
188 # Longer version
190 die Mojo::Exception->new('Something went wrong!')->trace;
191 trace
193 $e = $e->trace;
194 $e = $e->trace($skip);
195 Generate stack trace and store all "frames", defaults to skipping 1
197 call frame.
198 # Skip 3 call frames
200 $e->trace(3);
201 # Skip no call frames
203 $e->trace(0);
204
206 Mojo::Exception overloads the following operators.
207 bool
209 my $bool = !!$e;
210 Always true.
212 stringify
214 my $str = "$e";
215 Alias for "to_string".
217
219 Mojolicious, Mojolicious::Guides, <https://mojolicious.org>.
220perl v5.30.1 2020-01-30 Mojo::Exception(3)