Part IV. 4. Trigger Creation in Salesforce

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Writing Apex Triggers

Apex triggers enable you to perform custom actions before or after events to records in Salesforce, such as insertions, updates, or deletions. Just like database systems support triggers, Apex provides trigger support for managing records.

Typically, you use triggers to perform operations based on specific conditions, to modify related records or restrict certain operations from happening. You can use triggers to do anything you can do in Apex, including executing SOQL and DML or calling custom Apex methods.

Use triggers to perform tasks that can’t be done by using the point-and-click tools in the Salesforce user interface. For example, if validating a field value or updating a field on a record, use validation rules and workflow rules instead.

Triggers can be defined for top-level standard objects, such as Account or Contact, custom objects, and some standard child objects. Triggers are active by default when created. Salesforce automatically fires active triggers when the specified database events occur.

Trigger Syntax

The syntax of a trigger definition is different from a class definition’s syntax. A trigger definition starts with the triggerkeyword. It is then followed by the name of the trigger, the Salesforce object that the trigger is associated with, and the conditions under which it fires. A trigger has the following syntax:
trigger TriggerName on ObjectName (trigger_events) {
code_block
}

Please refer the following link to learn more about trigger programming How to show error message in trigger .

To execute a trigger before or after insert, update, delete, and undelete operations, specify multiple trigger events in a comma-separated list. The events you can specify are:
  • before insert
  • before update
  • before delete
  • after insert
  • after update
  • after delete
  • after undelete

Example

This simple trigger fires before you insert an account and writes a message to the debug log.

  1. In the Developer Console, click File | New | Apex Trigger.
  2. Enter HelloWorldTrigger for the trigger name, and then select Account for the sObject. Click Submit.
  3. Replace the default code with the following.

trigger HelloWorldTrigger on Account (before insert) {
System.debug(‘Hello World!’);
}

4. To save, press Ctrl+S.

5. To test the trigger, create an account.

Click Debug | Open Execute Anonymous Window.

In the new window, add the following and then click Execute.

Account a = new Account(Name=’Test Trigger’);
insert a;

6.In the debug log, find the Hello World! statement. The log also shows that the trigger has been executed.

Types of Triggers

There are two types of triggers.

  • Before triggers are used to update or validate record values before they’re saved to the database.
  • After triggers are used to access field values that are set by the system (such as a record’s Id or LastModifiedDate field), and to affect changes in other records. The records that fire the after trigger are read-only.

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This training information is very useful to learn about Trigger creation in salesforce.