Triggers in Salesforce

Triggers in Salesforce - Get Started

What is a Trigger?

A Trigger is an Apex script, which we can use in many situations. The use of trigger is, it will help you to call a specific piece of code when something happens in Salesforce org. Eg: Record inserted / Record edited / Record deleted etc. In such cases, we can use Trigger.

What is Trigger Syntax?

Trigger TriggerName on ObjectName (Trigger Events) {
    Code block
}

Types of Triggers

There are two types of triggers:

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  • Before Triggers - In this type of trigger, code is executed before the record gets saved in the database.
  • After Triggers - In this type of trigger, code is executed after the record gets saved in the database.

dont miss out iconDon't forget to check out: Deleting Apex Classes / Apex Triggers From Production Using Workbench | Salesforce Tutorial

Trigger Context Variables

  • isInsert - Returns true if the trigger got fired because of the insert operation.
  • isUpdate - Returns true if the trigger got fired because of the update operation.
  • isDelete - Returns true if the trigger got fired because of the delete operation.
  • isBefore - Returns true if the trigger got fired before any record was saved in the database.
  • isAfter - Returns true if the trigger got fired after all records were saved in the database.
  • isUndelete - If a record gets recovered after deletion it returns true.
  • isExecuting -  if the current context for the Apex code is only a trigger, it returns true.
  • new - Returns a list of records with new versions of them.
  • old - It gives a list of old versions of the records in return.
  • newMap - Map of new versions of the records.
  • oldMap - It is a Map of old versions of the records.
  • size - The total number of records in both trigger old and trigger new.

Trigger Events

  • beforeinsert
  • afterinsert
  • beforeupdate
  • afterupdate
  • beforedelete
  • afterdelete
  • afterundelete

Example Code

Requirement: Show error on duplicate contact creation.

Handler class code: 

public class DuplicateContactErrorHandler {
    public static void DuplicateContactErrorMethod(List<Contact> contactList){ //created a list of contacts in method
        Set<String> new_EmailSet = new Set<String>(); //set for new email strings
        Set<String> existingEmailSet = new Set<String>(); //set for existing email string        
        for ( Contact con : contactList ) { //for loop on contact
            if ( con.Email != null ) { //checking if email field is null or not
                newEmailSet.add(con.Email); //if not null then email is added in the set
            }
        }
        //query to call existing contacts with email
        List<Contact> existing_ContactsList = [Select Id, Email From Contact Where Email IN: new_EmailSet AND Email != null];        
        for (Contact con : existing_ContactsList ) { //for loop on existing contact list
            existingEmailSet.add(con.Email); //email ids added in the existing email set
        }
        for ( Contact con : contactList ) { //for loop on new contact list
            if ( existingEmailSet.contains( con.Email ) ) { //if email matches email in the existing set
                con.Email.AddError(' Duplicate Email is not Allowed '); //contact will not be saved, it will show error
            } 
            else {
                existingEmailSet.add(con.Email); //else it's email will be saved in existing email set
            }
        }
    }
}

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Trigger Code:

trigger Duplicate_Contact_Error_Trigger on Contact (before insert, before update) {
    if(Trigger.isinsert || Trigger.isupdate){
        DuplicateContactErrorHandler.DuplicateContactErrorMethod(trigger.new);
    }
}

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