Workflows, triggers and events
This page is for application creators who run their own logic when something happens: before content is published, after a user registers, at checkout. Exponential offers two mechanisms: workflows (configured by administrators, built from event types) and kernel event listeners (code). The administrator's guide is Workflows.
Contents
- The pieces
- Operations you can hook
- How a process runs
- Workflow or event listener?
- Setting it up for an application
The pieces
| Term | What |
|---|---|
| Workflow | a named list of events, in a workflow group (Setup > Workflows) |
| Event type | a class that does one step: approve, wait until date, multiplexer, payment gateway, simple shipping, finish user register, and those of extensions |
| Trigger | connects a workflow to an operation, before or after it (Setup > Triggers) |
| Process | one run of a workflow for one object and version, kept while it waits |
Operations you can hook
settings/workflow.ini [OperationSettings] AvailableOperationList[] lists the operations that offer triggers. Shipped
active: content_publish, before_shop_confirmorder, shop_checkout, shop_addtobasket, shop_updatebasket. More are
listed commented out (content_move, content_hide, content_delete, content_updatesection, content_read,
content_updateobjectstate, user_activation, user_password ...); enable one in an override to use it.
How a process runs
- The operation reaches its trigger and starts the workflow.
- Each event's
execute()returns a status: accepted (go on), rejected (stop the operation), deferred to cron (wait), fetch template (show a page), redirect, cancelled. - A deferred process is run again by the
workflow.phpcronjob (partfrequent); without it, waiting content never publishes. - When the last event accepts, the held-back operation finishes.
Waiting processes are listed in Setup > Workflow processes (/workflow/processlist).
Workflow or event listener?
| Use a workflow when | Use a kernel event listener when |
|---|---|
| administrators should switch it on and off, or order steps | the behavior is always part of your application |
| the step may wait (approval, payment, a date) | it must run synchronously and never wait |
| it is tied to one of the trigger operations | the event has no trigger (a site.ini [Event] Listeners[] event) |
Kernel events and filter events are listed in Extension points; filter listeners must return the value they receive. See also the event hook pattern.
Setting it up for an application
- Write the event type (Writing a workflow event type).
- Ship a setup step or instructions: create the workflow, add the event, connect the trigger.
- Make sure the
frequentcron part runs if any event defers to cron. - Test publish with and without the workflow; test cancel in Setup > Workflow processes.
Related pages
- Writing a workflow event type
- Object states
- Workflow event pattern
- Free documentation: this page is free to copy, translate and improve under the GNU FDL 1.3.
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