Trigger Framework Overview

The trigger framework separates three concerns that are usually tangled together in a single trigger: the trigger itself, the pipeline that decides which handlers run, and the handlers that hold the actual logic.

How it fits together

1. The trigger: a one-line trigger on your object that constructs a TriggerPipeline for the object's SObjectType. See Creating a pipeline.
2. Trigger_Pipeline__mdt: a custom metadata record that tells the pipeline which contexts (before insert, after update, and so on) are enabled for the object.
3. Trigger_Handler__mdt: one custom metadata record per handler, naming the handler class and which contexts it participates in.
4. The handler: a class extending ATriggerHandler, overriding only the context methods it needs. See Creating a handler.

Because the wiring lives in custom metadata, adding, removing, or reordering handlers on an object never requires touching the trigger or redeploying Apex. It's a metadata change.

Supported trigger contexts

• Before Insert
• After Insert
• Before Update
• After Update
• Before Delete
• After Delete
• After Undelete

DML

Handlers should not perform DML directly. Route inserts, updates, and deletes through the DML utility instead, so multiple handlers writing to the same object in one pipeline execution collapse into a single DML statement. See DML utility.