1Workflow::Condition(3)User Contributed Perl DocumentationWorkflow::Condition(3)
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6 Workflow::Condition - Evaluate a condition depending on the workflow
7 state and environment
8
10 # First declare the condition in a 'workflow_condition.xml'...
11 <conditions>
13 <condition
14 name="IsAdminUser"
15 class="MyApp::Condition::IsAdminUser">
16 <param name="admin_group_id" value="5" />
17 <param name="admin_group_id" value="6" />
18 </condition>
19 ...
20 # Reference the condition in an action of the state/workflow definition...
22 <workflow>
23 <state>
24 ...
25 <action name="SomeAdminAction">
26 ...
27 <condition name="IsAdminUser" />
28 </action>
29 <action name="AnotherAdminAction">
30 ...
31 <condition name="IsAdminUser" />
32 </action>
33 <action name="AUserAction">
34 ...
35 <condition name="!IsAdminUser" />
36 </action>
37 </state>
38 ...
39 </workflow>
40 # Then implement the condition
42 package MyApp::Condition::IsAdminUser;
44 use strict;
46 use base qw( Workflow::Condition );
47 use Workflow::Exception qw( condition_error configuration_error );
48 __PACKAGE__->mk_accessors( 'admin_group_id' );
50 sub _init {
52 my ( $self, $params ) = @_;
53 unless ( $params->{admin_group_id} ) {
54 configuration_error
55 "You must define one or more values for 'admin_group_id' in ",
56 "declaration of condition ", $self->name;
57 }
58 my @admin_ids = $self->_normalize_array( $params->{admin_group_id} );
59 $self->admin_group_id( { map { $_ => 1 } @admin_ids } );
60 }
61 sub evaluate {
63 my ( $self, $wf ) = @_;
64 my $admin_ids = $self->admin_group_id;
65 my $current_user = $wf->context->param( 'current_user' );
66 unless ( $current_user ) {
67 condition_error "No user defined, cannot check groups";
68 }
69 foreach my $group ( @{ $current_user->get_groups } ) {
70 return if ( $admin_ids->{ $group->id } );
71 }
72 condition_error "Not member of any Admin groups";
73 }
74
76 Conditions are used by the workflow to see whether actions are avail‐
77 able in a particular context. So if user A asks the workflow for the
78 available actions she might get a different answer than user B since
79 they determine separate contexts.
80 NOTE: The condition is enforced by Workflow::State. This means that the
82 condition name must be visible inside of the state definition. If you
83 specify the reference to the condition only inside of the full action
84 specification in a seperate file then nothing will happen. The refer‐
85 ence to the condition must be defined inside of the state/workflow
86 specification.
87
89 Strategy
90 The idea behind conditions is that they can be stateless. So when the
92 Workflow::Factory object reads in the condition configuration it cre‐
93 ates the condition objects and initializes them with whatever informa‐
94 tion is passed in.
95 Then when the condition is evaluated we just call "evaluate()" on the
97 condition. Hopefully the operation can be done very quickly since the
98 condition may be called many, many times during a workflow lifecycle --
99 they are typically used to show users what options they have given the
100 current state of the workflow for things like menu options. So keep it
101 short!
102 Methods
104 To create your own condition you should implement the following:
106 _init( \%params )
108 This is optional, but called when the condition is first initialized.
110 It may contain information you will want to initialize your condition
111 with in "\%params", which are all the declared parameters in the condi‐
112 tion declartion except for 'class' and 'name'.
113 You may also do any initialization here -- you can fetch data from the
115 database and store it in the class or object, whatever you need.
116 If you do not have sufficient information in "\%params" you should
118 throw an exception (preferably 'configuration_error' imported from
119 Workflow::Exception).
120 evaluate( $workflow )
122 Determine whether your condition fails by throwing an exception. You
124 can get the application context information necessary to process your
125 condition from the $workflow object.
126 #=head3 init
128 Caching and inverting the result
130 If in one state, you ask for the same condition again, Workflow uses
132 the cached result, so that within one list of available actions, you
133 will get a consistent view. Note that if we would not use caching, this
134 might not necessary be the case, as something external might change
135 between the two evaluate() calls.
136 Caching is also used with an inverted condition, which you can specify
138 in the definition using "<condition name="!some_condition"">. This
139 condition returns exactly the opposite of the original one, i.e. if
140 the original condition fails, this one does not and the other way
141 round. As caching is used, you can model "yes/no" decisions using this
142 feature - if you have both "<condition name="some_condition""> and
143 "<condition name="!some_condition""> in your workflow state definition,
144 exactly one of them will succeed and one will fail - which is particu‐
145 larly useful if you use "autorun" a lot.
146
148 Copyright (c) 2003-2004 Chris Winters. All rights reserved.
149 This library is free software; you can redistribute it and/or modify it
151 under the same terms as Perl itself.
152
154 Chris Winters <chris@cwinters.com>
155perl v5.8.8 2007-04-25 Workflow::Condition(3)