יובל קוג'מן (Yuval Kogman) > Class-Workflow > Class::Workflow::Context

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NAME ^

Class::Workflow::Context - The context in which a transition is being applied (optional).

SYNOPSIS ^

        use Class::Workflow::Context; # or a subclass or something

        my $c = Class::Workflow::Context->new( ... );

        my $new_instance = $transition->apply( $instance, $c );

DESCRIPTION ^

If you need to pass arbitrary arguments to the workflow, a context object will usually help.

This specific context object provides stash, a writable hash which is essentially free-for-all.

Class::Workflow::Context doesn't provide much and should generally be subclassed. It is designed to resemble the Catalyst context object.

Usage of a context object is completely optional, and Class::Workflow's other core objects (Class::Workflow::State, Class::Workflow::Transition, and Class::Workflow::Instance really don't care about context objects at all).

STYLE GUIDE ^

When writing a workflow that governs a web application, for example, transitions will generally expect explicit parameters, having to do with their specific responsibility, and more "global" parameters, like on behalf of which user is this transition being applied.

A context object is a way to provide a standard set of facilities that every transition can expect.

        sub apply {
                my ( $self, $instance, $c, %args ) = @_;

                my $arg = $args{arg_i_care_about};

                my $user = $c->user;

                ...
        }

Conceptually $c is akin to the environment the workflow is being used in, wheras %args are the actual parameters.

Note that this is only one of many possible conventions you can use in your workflow system.

The context should probably not be mutated by the workflow itself. That's what the workflow instance is for.

CONTEXT ROLES ^

You are encouraged to create roles for additional paremeters in the context, and compose them together into the final workflow class instead of relying on stash.

This provides a more structured approach, and lets you use lazy_build in the attributes cleanly.

You could also apply runtime roles to the workflow class for a more dynamic and flexible solution.

FIELDS ^

stash

Just a simple hash reference.

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