Episode 5 - Demystifying Apex Triggers

Episode 5 – Demystifying Apex Triggers

Posted on January 26, 2020 Posted By: Amit Chaudhary Categories: Apex, Apex Hours for Students, Salesforce Developer, Salesforce Developer Training

In this post we will learn about writing triggers to fire business logic using Apex. Join us as you embark on this wonderful journey to become a champion Salesforce developer. Apex triggers within Salesforce are designed to help you automate certain tasks. Apex triggers allow you to perform custom actions before and after events in Salesforce. These events can include things such as data insertions, updates to existing data, or deletions.

What is Apex Trigger in Salesforce?

Trigger is a procedure in database which automatically invokes whenever a special events in Database occurs. Apex triggers enable you to perform custom actions before or after events to records in Salesforce, such as insertions, updates, or deletions.

What are different type of Triggers?

There are two types of triggers:

Before triggers are used to perform a task before a record is inserted or updated or deleted. These are used to update or validate record values before they are saved to the database.
After triggers are used if we want to use the information set by Salesforce system and to make changes in the other records. The records that fire the after trigger are read-only.

When Should we Use Trigger?

There lots of automation tool available in Salesforce. Lets understand the when to use Apex Trigger in Salesforce.

Complex logic incapable of being processed via declarative artifacts
Logic associated with DML
Operations on unrelated objects
Integration with External Systems

Trigger Events in Salesforce

A trigger is a set of statement which can be executed on the following events. We can add below events with comma-separated. Here is a list of trigger events in salesforce.

Trigger Context Variable

All triggers define implicit variables that allow developers to access run-time context. These variables are contained in the System.Trigger class

Variable	Usage
isExecuting	It tells if code current context is trigger or not
isInsert	It returns true if trigger fires on insert operation
isUpdate	It returns true if trigger fires on update operation
isDelete	It returns true if trigger fires on delete operation
isBefore	It returns true if code is running in Before context
isAfter	It returns true if code is running in After context
new	It holds list of new versions of sObject records *This sObject list is only available in insert, update, and undelete triggers, and the records can only be modified in before triggers*
newMap	It holds new versions of sObject in key value pair *This map is only available in before update, after insert, after update, and after undelete triggers*
old	It holds list of old versions of sObject records *This sObject list is only available in update and delete triggers*
oldMap	It holds old versions of sObject in key value pair *This map is only available in update and delete triggers.*
operationType	Returns an enum of type System.TriggerOperation corresponding to the current operation. System.TriggerOperation enum are: BEFORE_INSERT, BEFORE_UPDATE, BEFORE_DELETE,AFTER_INSERT, AFTER_UPDATE, AFTER_DELETE, and AFTER_UNDELETE
size	The total number of records in a trigger invocation, both old and new.

Example of Apex Trigger

Demo 1 : Using context variable in Trigger

Let see the first demo of context variable in Trigger.

trigger AccountTrigger on Account (before insert, before update, after update) {
    if(Trigger.isBefore && Trigger.isInsert){
        System.debug('I am in AccountTrigger before insert context');
    }
    if(Trigger.isUpdate){
        if(Trigger.isBefore){
            for(Account acc :Trigger.new){
                System.debug('New Name'+ acc.Name);
                System.debug('Old Name'+ Trigger.oldMap.get(acc.Id).Name);
            }
        }
    }
}

Recording

Check our our recording for the session.

Trigger Handler pattern

Check this blog post to learn about which all trigger pattern are available in Salesforce. For Trigger Handler code check this post.

Check below ode how to write trigger handler pattern.

Create one Trigger “AccountTrigger“

trigger AccountTrigger on Account( after insert, after update, before insert, before update){
    AccountTriggerHandler handler = new AccountTriggerHandler(Trigger.isExecuting, Trigger.size);   
    if( Trigger.isInsert ){
        if(Trigger.isBefore){
            handler.OnBeforeInsert(trigger.New);
        }
        else{
            handler.OnAfterInsert(trigger.New);
        }
    }
    else if ( Trigger.isUpdate ){
        if(Trigger.isBefore){ handler.OnBeforeUpdate(trigger.New,trigger.Old,Trigger.NewMap,Trigger.OldMap);
        }
        else{
      handler.OnAfterUpdate(trigger.New,trigger.Old,Trigger.NewMap,Trigger.OldMap);
        }
    }
}

Create one Trigger Handler Class



public with sharing class AccountTriggerHandler 
{
    private boolean m_isExecuting = false;
    private integer BatchSize = 0;
    public static boolean IsFromBachJob ;
    public static boolean isFromUploadAPI=false;
    
    public AccountTriggerHandler(boolean isExecuting, integer size){
        m_isExecuting = isExecuting;
        BatchSize = size;
    }
            

    public void OnBeforeInsert(List<Account> newAccount){
        system.debug('Account Trigger On Before Insert');
    }
    public void OnAfterInsert(List<Account> newAccount){
        system.debug('Account Trigger On After Insert');
    }
    public void OnAfterUpdate( List<Account> newAccount, List<Account> oldAccount, Map<ID, Account> newAccountMap , Map<ID, Account> oldAccountMap ){
        system.debug('Account Trigger On After Update ');
        AccountActions.updateContact (newAccount);
    }
    public void OnBeforeUpdate( List<Account> newAccount, List<Account> oldAccount, Map<ID, Account> newAccountMap , Map<ID, Account> oldAccountMap ){
        system.debug('Account Trigger On Before Update ');
    }

    @future 
    public static void OnAfterUpdateAsync(Set<ID> newAccountIDs){
    }      
    public boolean IsTriggerContext{
        get{ return m_isExecuting;}
    }
    
    public boolean IsVisualforcePageContext{
        get{ return !IsTriggerContext;}
    }
    
    public boolean IsWebServiceContext{
        get{ return !IsTriggerContext;}
    }
    
    public boolean IsExecuteAnonymousContext{
        get{ return !IsTriggerContext;}
    }
}

Create one Trigger Action Class

public without sharing class AccountActions{
    public static void updateContact ( List<Account> newAccount){   
        // Add your logic here
    }
}

Trigger Best Practice

One Trigger Per Object : A single Apex Trigger is all you need for one particular object. If you develop multiple Triggers for a single object, you have no way of controlling the order of execution if those Triggers can run in the same contexts
Logic-less Triggers : If you write methods in your Triggers, those can’t be exposed for test purposes. You also can’t expose logic to be re-used anywhere else in your org.
Context-Specific Handler Methods : Create context-specific handler methods in Trigger handlers
Bulkify your Code : Bulkifying Apex code refers to the concept of making sure the code properly handles more than one record at a time.
Avoid SOQL Queries or DML statements inside FOR Loops : An individual Apex request gets a maximum of 100 SOQL queries before exceeding that governor limit. So if this trigger is invoked by a batch of more than 100 Account records, the governor limit will throw a runtime exception.
Using Collections, Streamlining Queries, and Efficient For Loops : It is important to use Apex Collections to efficiently query data and store the data in memory. A combination of using collections and streamlining SOQL queries can substantially help writing efficient Apex code and avoid governor limits.
Querying Large Data Sets : The total number of records that can be returned by SOQL queries in a request is 50,000. If returning a large set of queries causes you to exceed your heap limit, then a SOQL query for loop must be used instead. It can process multiple batches of records through the use of internal calls to query and queryMore
Use @future Appropriately : It is critical to write your Apex code to efficiently handle bulk or many records at a time. This is also true for asynchronous Apex methods (those annotated with the @future keyword). The differences between synchronous and asynchronous Apex can be found
Avoid Hardcoding IDs : When deploying Apex code between sandbox and production environments, or installing Force.com AppExchange packages, it is essential to avoid hardcoding IDs in the Apex code. By doing so, if the record IDs change between environments, the logic can dynamically identify the proper data to operate against and not fail

Trigger Order of Execution

Here is recording of our old session on Order of Execution. Check this blog post to learn more.

Always remember below points before writing trigger :-
1) Order Of Execution
2) Learn about Other Trigger Framework

Assignment

Create Custom object Invoice with field Total Amount
Create child object Invoice Line Item with Lookup relationship to Invoice.
Add price field into Invoice Line Item.
Write trigger on Invoice Line Item which will add some of all child records to parent Invoice

Further Learning

Apex Trigger

Trigger Framework

Learn how to completely and cleanly control your Apex code with Trigger Frameworks, why they’re useful, and the various ways to implement them. In this session will talk about Apex Trigger Framework in Salesforce and benefit of using a trigger framework, How many trigger framework are available, which one is lightweight apex trigger framework and Comparison of different approaches.

Don’t forget to register for our next session on Test Classes. Check this post for all other session detail.

Make sure to subscribe our YouTube channel to get notification for video upload. So, learn at your pace and free will and ace your journey to Salesforce!

Amit Chaudhary

Amit Chaudhary is Salesforce Application & System Architect and working on Salesforce Platform since 2010. He is Salesforce MVP since 2017 and have 17 Salesforce Certificates.

He is a active blogger and founder of Apex Hours.

Demystifying Apex Triggers, Trigger Events, Trigger Handler pattern

Comments(30)

Reply
Ankit Desai says:
February 15, 2020 at 7:25 am
Completed Assignment for Day 5
I have created one trigger “InvoiceAmountUpdate” and one class “InvoiceAmountUpdateHandler”
Reply
Aathirai says:
February 16, 2020 at 11:59 am
Completed Day 5 Assignment
Reply
A Belano says:
February 17, 2020 at 7:16 am
Day 5 Assignment Completed
Reply
Brisilda says:
February 17, 2020 at 10:24 am
Episode 5 – Demystifying Apex Triggers Assignment Completed!
Reply
Archit Dutt Sharma says:
February 17, 2020 at 12:29 pm
Completed Day 5 assignment
Reply
Anuj Sahu says:
February 17, 2020 at 12:30 pm
Day 5 Assignment is completed
Reply
Marishell Cruz says:
February 20, 2020 at 6:48 am
completed
- Reply
  Amit Chaudhary says:
  February 24, 2020 at 10:07 pm
  8 more to go
- Reply
  Pb says:
  March 1, 2020 at 5:45 pm
  Can someone update all the solution?
Reply
Jaya Iyer says:
February 26, 2020 at 3:12 am
completed assignment 5
Reply
Pb says:
March 1, 2020 at 5:46 pm
Solution plz
- Reply
  Amit Chaudhary says:
  March 4, 2020 at 11:52 pm
  After contest over
Reply
Arjinder Kaur says:
March 5, 2020 at 3:30 am
assignment 5 completed
Reply
Pritam Pramod Dalvi says:
March 12, 2020 at 5:59 pm
Assignment 5 Completed
Reply
NARESH CHANDA says:
March 13, 2020 at 9:08 pm
Day 5 Assignment is completed
Reply
ASHOK KUMAR PANIGRAHI says:
April 1, 2020 at 1:16 am
Day 5 Assignment is completed
Reply
Arjinder Kaur says:
April 7, 2020 at 1:45 am
Solution for Assignment : Trigger on Invoice Line Item which will add sum of all child records to parent Invoice:

trigger AddInvoiceItems on Invoice_Line_Item__c ( after insert, after update, after delete ) {

List ListIds = new List();

if ( Trigger.isInsert || Trigger.isUpdate ) {

for ( Invoice_Line_Item__c item : Trigger.New ) {
if ( Trigger.isInsert || ( Trigger.isUpdate && Trigger.OldMap.get(item.ID).price__c!=item.price__c) ) {

listIds.add(item.Invoice__c);

}
}
}

if(Trigger.isDelete)
{
for( Invoice_Line_Item__c item : Trigger.Old ) {

listIds.add(item.Invoice__c);

}
}

Map TotalPriceMap = new Map();

for ( Invoice_Line_Item__c item : [ SELECT Id, price__c, invoice__c FROM Invoice_Line_Item__c WHERE invoice__c IN : ListIds ] ) {

Decimal totalPrice = 0;
if( TotalPriceMap.containsKey ( item.invoice__c ) )
totalPrice = TotalPriceMap.get( item.invoice__c );
totalPrice = totalPrice + item.price__c;
TotalPriceMap.put(item.invoice__c,totalPrice);
}

List updateInvoice = new List();
for ( Id invoiceId : TotalPriceMap.KeySet() ) {
Invoice__c inv = new Invoice__c ( Id = invoiceId );
inv.Total_Amount__c = TotalPriceMap.get( invoiceId );
updateInvoice.add(inv);
}

if ( updateInvoice.size() > 0 )
Update updateInvoice;

}
- Reply
  kishore goud says:
  April 7, 2020 at 6:12 am
  HI bro, i have one question, you have declared empty map . since it is empty how you are searching using containskey
  - Reply
    Arjinder Kaur says:
    April 10, 2020 at 5:38 pm
    Thanks for pointing out. It should be like this:
    
    Map TotalPriceMap = new Map();
    
    I believe, datatype got missed while I pasted my solution.
    I am sorry about it. I will check and correct it.
    
    Thanks again!
- Reply
  Arjinder Kaur says:
  April 10, 2020 at 9:23 pm
  Corrections to the code – Please check comments below
Reply
kishore goud says:
April 7, 2020 at 6:12 am
HI bro, i have one question, you have declared empty map . since it is empty how you are searching using containskey
- Reply
  Arjinder Kaur says:
  April 10, 2020 at 6:01 pm
  Facing some issue with code within angle brackets after I posted comment.
  
  Correction:
  List ListIds = new List(); // Id within angle brackets after List
  Map TotalPriceMap = new Map(); // Id,Decimal within angle brackets after Map
  List updateInvoice = new List(); // Invoice__c within angle brackets after List
Reply
Arjinder Kaur says:
April 10, 2020 at 6:07 pm
Noticed some issues with posted code : I noticed code(data type) within angle brackets got removed after I posted it. I am sorry about this.
Please add following datatype ( written after backslash ) within angle bracket after List or Map

Correction:

List ListIds = new List(); // Add Id within angle brackets after List

Map TotalPriceMap = new Map(); // Add Id , Decimal within angle brackets after Map

List updateInvoice = new List(); // Add Invoice__c within angle brackets after List
Reply
Ankit Desai says:
April 10, 2020 at 9:02 pm
Code for Assignment Day 5
——————————–

trigger InvoiceAmountUpdate on Invoice_Line_Item__c (after insert,
after update,
after delete) {

String invoiceId = ”;
if(Trigger.isInsert || Trigger.isUpdate) {
for(Invoice_Line_Item__c invoiceLineItem : Trigger.new) {
if(invoiceLineItem.Invoice__c != null) {
invoiceId = invoiceLineItem.Invoice__c;
}
}
}
if(Trigger.isDelete){
for(Invoice_Line_Item__c invoiceLineItem : Trigger.old) {
if(invoiceLineItem.Invoice__c != null) {
invoiceId = invoiceLineItem.Invoice__c;
}
}
}
if(invoiceId != ”) {
InvoiceAmountUpdateHandler.updateInvoiceAmount(invoiceId);
}
}

—————————————————————————–

public class InvoiceAmountUpdateHandler {
public static void updateInvoiceAmount(String invoiceId) {
List items = new List();
items = [select Id,price__c from Invoice_Line_Item__c where Invoice__c = :invoiceId];
Decimal amount = 0;
for(Invoice_Line_Item__c item : items) {
amount = amount + item.Price__c;
}
Invoice__c invoice = new Invoice__c();
invoice.Id = invoiceId;
invoice.Total_Amount__c = amount;
update invoice;

}
}
- Reply
  swathi says:
  May 21, 2020 at 5:58 am
  Hi! I have written a code for trigger assignment task and its working well for insert and update. Can you please tell me whether I need to modify my code for better results..
  
  Parent: Invoice__c
  Child: Invoice_Line_Item__c
  
  Trigger code:
  trigger Invoice_Line_Item__cTrigger on Invoice_Line_Item__c (after insert, after Update) {
  
  if((trigger.IsInsert == true && Trigger.Isafter == true) ||(trigger.IsUpdate == true && Trigger.Isafter == true)){
  
  Invoice_Line_ItemHandler.AmoutUpd(trigger.new);
  }
  }
  
  APEXHANDLER::
  
  public class Invoice_Line_ItemHandler {
  
  public static list P_id = new list();
  public static decimal amount=0;
  
  public static void AmoutUpd(list ChildRec){
  
  for(Student__c Pid : StuRec){
  
  if(pid.Teacher_name__c != null){
  
  P_id.add(pid.Invoice_name__c);
  }
  }
  list Rec = [SELECT Total_amout__c,name,(SELECT Invoice_name__c,price__c FROM Invoice_Line_Item__r) FROM Invoice__c WHERE ID IN :P_id];
  
  for(Invoice__c a: Rec){
  
  for(Invoice_Line_Item__c b: a.Invoice_Line_Item__r){
  
  amount = amount+ b.price__c ;
  }
  
  a.Total_amout__c = amount;
  }
  update Rec;
  }
  
  }
- Reply
  sapna says:
  November 18, 2021 at 7:09 am
  Hey, if we want to delete some record from Invoice line item and again add the record in Invoice line item and i have created one more filed at Invoice line item that is count of line Item in particular Invoice then count should be increase… how to do it??
Reply
Jim says:
July 2, 2020 at 4:31 am
hello
I copied the Handler Class from above into the Dev console but I receive Unexpected token ‘List’. error for this statement:
List items = new List();

What am i missing here?

-jim
Reply
Kiran says:
July 9, 2020 at 6:10 am
Logic for Trigger
================
public class ApexHourTriggerAssignment {

public static void updateInvoceObjectField(List lstinvln){
Decimal amount=0;
Set liStIds = new Set();
for (Invoice_Line_Up__c ilu :lstinvln) {
if(ilu.Invoice_Name__c != null) {
liStIds.add(ilu.Invoice_Name__c);
}
}
List ListInvoice = [Select id, Total_Amount__c, (select id, price__c from Invoices_Line_up__r)
from Invoice__c Where Id IN :liStIds];
ListListInv = new List();
For(Invoice__c inv : ListInvoice){
for(Invoice_Line_Up__c ilu1 : inv.Invoices_Line_up__r){
amount = amount + ilu1.price__c;
}
inv.Total_Amount__c = amount;
ListInv.add(inv);
}
update ListInv;
}
}

======================
trigger ApexHourTriggerAssignmentTrigger on Invoice_Line_Up__c (After insert,After Update) {

ApexHourTriggerAssignment.updateInvoceObjectField(Trigger.new);
}
- Reply
  Amit Chaudhary says:
  July 10, 2020 at 3:03 am
  Keep learning
Reply
Sagar says:
February 21, 2021 at 3:14 pm
My solution for assignment.

trigger TotalInvoiceAmount on Invoice_Line_Item__c (after insert) {

Map UniqueInvoiceToUpdate = new map(); // To maintain unique sobject to be updated
Map TotalAMount = new Map(); // To maintain the updated amount of each invoice sobject

ListInvoiceToUpdate = new List(); // final list to perform dml update operation
Invoice__c ParentInvoice;

for (Invoice_Line_Item__c currentInvoiceItem : Trigger.New) {

ParentInvoice = [select id, Total_Amount__c from Invoice__c where Id = :currentInvoiceItem.Invoice__c LIMIT 1][0];

// Check if we have updated total value of invoice in previous iterations:
if (TotalAmount.get(ParentInvoice.Id) != null) {

// if yes, add the current amount of invoice line item to the previous updated invoice object.
// Not that, we have not commit to database yet. Hence we are retrieving updated amount from map and not from sobject’s Total amount field
ParentInvoice.Total_Amount__c = TotalAmount.get(ParentInvoice.Id) + currentInvoiceItem.Amount__c;
}
else {
// We haven’t saved total amount in map yet.
// Add current invoice line item amount to total amount of invoice object.
ParentInvoice.Total_Amount__c += currentInvoiceItem.Amount__c;
}
// save updated total amount of invoice object in map
TotalAmount.put(ParentInvoice.Id, ParentInvoice.Total_Amount__c );

// update invoice object’s map.
UniqueInvoiceToUpdate.put(ParentInvoice.Id, ParentInvoice);
}

// iterate UniqueInvoiceToUpdate map to put those invoice objects in list.
for (Invoice__c I : UniqueInvoiceToUpdate.values()){
InvoiceToUpdate.add(I);
}

// update list.
update InvoiceToUpdate;
}

Any better solution?

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Episode 5 – Demystifying Apex Triggers

What is Apex Trigger in Salesforce?

What are different type of Triggers?

When Should we Use Trigger?

Trigger Events in Salesforce

Trigger Context Variable

Example of Apex Trigger

Recording

Trigger Handler pattern

Trigger Best Practice

Trigger Order of Execution

Assignment

Further Learning

Trigger Framework

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Comments(30)

Ankit Desai says:

Aathirai says:

A Belano says:

Brisilda says:

Archit Dutt Sharma says:

Anuj Sahu says:

Marishell Cruz says:

Amit Chaudhary says:

Pb says:

Jaya Iyer says:

Pb says:

Amit Chaudhary says:

Arjinder Kaur says:

Pritam Pramod Dalvi says:

NARESH CHANDA says:

ASHOK KUMAR PANIGRAHI says:

Arjinder Kaur says:

kishore goud says:

Arjinder Kaur says:

Arjinder Kaur says:

kishore goud says:

Arjinder Kaur says:

Arjinder Kaur says:

Ankit Desai says:

swathi says:

sapna says:

Jim says:

Kiran says:

Amit Chaudhary says:

Sagar says:

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