1Workflow::Condition(3)User Contributed Perl DocumentationWorkflow::Condition(3)
2
6 Workflow::Condition - Evaluate a condition depending on the workflow
7 state and environment
8
10 This documentation describes version 1.54 of this package
11
13 # First declare the condition in a 'workflow_condition.xml'...
14 <conditions>
16 <condition
17 name="IsAdminUser"
18 class="MyApp::Condition::IsAdminUser">
19 <param name="admin_group_id" value="5" />
20 <param name="admin_group_id" value="6" />
21 </condition>
22 ...
23 # Reference the condition in an action of the state/workflow definition...
25 <workflow>
26 <state>
27 ...
28 <action name="SomeAdminAction">
29 ...
30 <condition name="IsAdminUser" />
31 </action>
32 <action name="AnotherAdminAction">
33 ...
34 <condition name="IsAdminUser" />
35 </action>
36 <action name="AUserAction">
37 ...
38 <condition name="!IsAdminUser" />
39 </action>
40 </state>
41 ...
42 </workflow>
43 # Then implement the condition
45 package MyApp::Condition::IsAdminUser;
47 use strict;
49 use base qw( Workflow::Condition );
50 use Workflow::Exception qw( condition_error configuration_error );
51 __PACKAGE__->mk_accessors( 'admin_group_id' );
53 sub _init {
55 my ( $self, $params ) = @_;
56 unless ( $params->{admin_group_id} ) {
57 configuration_error
58 "You must define one or more values for 'admin_group_id' in ",
59 "declaration of condition ", $self->name;
60 }
61 my @admin_ids = $self->_normalize_array( $params->{admin_group_id} );
62 $self->admin_group_id( { map { $_ => 1 } @admin_ids } );
63 }
64 sub evaluate {
66 my ( $self, $wf ) = @_;
67 my $admin_ids = $self->admin_group_id;
68 my $current_user = $wf->context->param( 'current_user' );
69 unless ( $current_user ) {
70 condition_error "No user defined, cannot check groups";
71 }
72 foreach my $group ( @{ $current_user->get_groups } ) {
73 return if ( $admin_ids->{ $group->id } );
74 }
75 condition_error "Not member of any Admin groups";
76 }
77
79 Conditions are used by the workflow to see whether actions are
80 available in a particular context. So if user A asks the workflow for
81 the available actions she might get a different answer than user B
82 since they determine separate contexts.
83 NOTE: The condition is enforced by Workflow::State. This means that the
85 condition name must be visible inside of the state definition. If you
86 specify the reference to the condition only inside of the full action
87 specification in a seperate file then nothing will happen. The
88 reference to the condition must be defined inside of the state/workflow
89 specification.
90
92 While some conditions apply to all workflows, you may have a case where
93 a condition has different implementations for different workflow types.
94 For example, IsAdminUser may look in two different places for two
95 different workflow types, but you want to use the same condition name
96 for both.
97 You can accomplish this by adding a type in the condition
99 configuration.
100 <conditions>
102 <type>Ticket</type>
103 <condition
104 name="IsAdminUser"
105 class="MyApp::Condition::IsAdminUser">
106 <param name="admin_group_id" value="5" />
107 <param name="admin_group_id" value="6" />
108 </condition>
109 ...
110 The type must match a loaded workflow type, or the condition won't
112 work. When the workflow looks for a condition, it will look for a
113 typed condition first. If it doesn't find one, it will look for non-
114 typed conditions.
115
117 Strategy
118 The idea behind conditions is that they can be stateless. So when the
119 Workflow::Factory object reads in the condition configuration it
120 creates the condition objects and initializes them with whatever
121 information is passed in.
122 Then when the condition is evaluated we just call "evaluate()" on the
124 condition. Hopefully the operation can be done very quickly since the
125 condition may be called many, many times during a workflow lifecycle --
126 they are typically used to show users what options they have given the
127 current state of the workflow for things like menu options. So keep it
128 short!
129 Methods
131 To create your own condition you should implement the following:
132 init( \%params )
134 This is optional, but called when the condition is first initialized.
136 It may contain information you will want to initialize your condition
137 with in "\%params", which are all the declared parameters in the
138 condition declartion except for 'class' and 'name'.
139 You may also do any initialization here -- you can fetch data from the
141 database and store it in the class or object, whatever you need.
142 If you do not have sufficient information in "\%params" you should
144 throw an exception (preferably 'configuration_error' imported from
145 Workflow::Exception).
146 evaluate( $workflow )
148 Determine whether your condition fails by throwing an exception. You
150 can get the application context information necessary to process your
151 condition from the $workflow object.
152 _init
154 This is a dummy, please refer to "init"
156 Caching and inverting the result
158 If in one state, you ask for the same condition again, Workflow uses
159 the cached result, so that within one list of available actions, you
160 will get a consistent view. Note that if we would not use caching, this
161 might not necessary be the case, as something external might change
162 between the two evaluate() calls.
163 Caching is also used with an inverted condition, which you can specify
165 in the definition using "<condition name="!some_condition"">. This
166 condition returns the negation of the original one, i.e. if the
167 original condition fails, this one does not and the other way round. As
168 caching is used, you can model "yes/no" decisions using this feature -
169 if you have both "<condition name="some_condition""> and "<condition
170 name="!some_condition""> in your workflow state definition, exactly one
171 of them will succeed and one will fail - which is particularly useful
172 if you use "autorun" a lot.
173 Caching can be disabled by changing $Workflow::Condition::CACHE_RESULTS
175 to zero (0):
176 $Workflow::Condition::CACHE_RESULTS = 0;
178 All versions before 1.49 used a mechanism that effectively caused
180 global state. To address the problems that resulted (see GitHub issues
181 #9 and #7), 1.49 switched to a new mechanism with a cache per workflow
182 instance.
183 $class->evaluate_condition( $WORKFLOW, $CONDITION_NAME )
185 Users call this method to evaluate a condition; subclasses call this
187 method to evaluate a nested condition.
188 If the condition name starts with an '!', the result of the condition
190 is negated. Note that a side-effect of this is that the return value of
191 the condition is ignored. Only the negated boolean-ness is preserved.
192 This does implement a trick that is not a convention in the underlying
194 Workflow library: by default, workflow conditions throw an error when
195 the condition is false and just return when the condition is true. To
196 allow for counting the true conditions, we also look at the return
197 value here. If a condition returns zero or an undefined value, but did
198 not throw an exception, we consider it to be '1'. Otherwise, we
199 consider it to be the value returned.
200
202 Copyright (c) 2003-2021 Chris Winters. All rights reserved.
203 This library is free software; you can redistribute it and/or modify it
205 under the same terms as Perl itself.
206 Please see the LICENSE
208
210 Please see Workflow
211perl v5.34.0 2021-07-27 Workflow::Condition(3)