Apex Trigger In Salesforce - Get Started

The trigger is an apex code that executes before and after the DML operations.

Following are the DML operations:-

• Insert
• Update
• Delete
• Upsert
• Merge
• Undelete

The trigger is divided into two types:

• Before Trigger:- These triggers are used to update or validate record values before they are saved to the database.

• After Trigger:-These triggers are usually used to update or validate the value of records after they are saved to the database.

Types of events in the trigger:

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

Don't forget to check out: Concept of Virtual and Abstract Modifiers in Apex | Salesforce Developer Guide

Note:- We can not use ‘Before Undelete’ because in this situation we don’t have a record id in the database.

Let us take an example:-

Example 1:- Add TASk to the Opportunity whenever a new opportunity is created or updated with Stage name = Closed won.

Step 1:- Login into your Salesforce org. And open your developer console.

Step 2:- Create a new Apex Trigger on Opportunity having name AddTaskToOpportunity.

Step 3:- Paste the below code in your trigger page and save it.

trigger AddTaskToOpportunity on Opportunity (after insert,after update) {
    List<task> tasks=New List<task>();
    for(opportunity opp:trigger.new){
        if(opp.stagename=='closed won'){
            task t=new task(whatid=opp.id);
            tasks.add(t); 
        }
    }
    upsert tasks;
}

Now, you can check if the trigger is working fine or not just by creating a new opportunity and updating any record with Stage name = Closed Won. 

Example 2:- Update the Name of the account with Phone field value as the suffix of the account name (Account Name =Name+Phone) whenever the new account is created or updated.

Step 1:- Login into your Salesforce org. And open your developer console.

Step 2:- Create a new Apex Trigger on Account having the name UpdateNameWithPhone.

Step 3:- Paste the below code into your trigger page and save it.

trigger UpdateNameWithPhone on Account (before insert, before update) {
    List<String> accountNames = new List<String>{};
    for(Account a: Trigger.new){
       a.Name =a.Name+' '+ a.Phone;
    }
}

Check out another amazing blog by Anshu here: Learn About List and Set in Salesforce

Now, you can check if the trigger is working fine or not just by creating and updating an account.

Examle 3:- Send a mail to the current user whenever an account is created or updated with Rating = Hot.

Step 1:- Login into your Salesforce org. And open your developer console.

Step 2:- Create a new Apex Trigger on Account having name emailRating.

Step 3:- Paste the below code into your trigger page and save it.

trigger emailRating on Account(After insert,After update) {   
    For(Account acc:Trigger.new ){
        if(acc.Rating == 'Hot'){
            User curnt_user=[SELECT Email FROM User WHERE Id= :UserInfo.getUserId()] ;
            Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
            String[] toAddresses = new String[] {curnt_user.Email};
            mail.setToAddresses(toAddresses);
            mail.setSubject('Account Rating');
            mail.setPlainTextBody('Rating equals to hot');
            Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail}) ; 
        }
    }
}

Now, you can check if the trigger is working fine or not just by creating and updating an account with Rating = Hot. And then you can check your mailbox.