Episode 5 – Demystifying Apex Triggers
In this episode 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.
Agenda
- Order of Execution
- When & How Triggers are invoked
- Trigger Events
- Avoiding Recursive Trigger Calls
- Q & A
Most importantly don’t break a leg if you are overwhelmed with the pace of the live sessions. All Apex Hours for Student sessions will be recorded and will be available on our YouTube channel.
Please register here and follow our ApexHours website to get more notification.
What is Trigger?
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.
When Should we Use Trigger?
- Complex logic incapable of being processed via declarative artifacts
- Logic associated with DML
- Operations on unrelated objects
- Integration with External Systems
Trigger Events
Trigger Context Variable
| 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. |
Demo 1 : Using 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);
}
}
}
}Order of Execution.
Here is recording of our old session on Order of Execution. Check this blog post to learn more.
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
Trigger Best Practice
1) One Trigger Per Object
2) Logic-less Triggers
3) Context-Specific Handler Methods
4) Bulkify your Code
5) Avoid SOQL Queries or DML statements inside FOR Loops
6) Using Collections, Streamlining Queries, and Efficient For Loops
7) Querying Large Data Sets
8) Use @future Appropriately
9) Avoid Hardcoding IDs
Always remember below points before writing trigger :-
1) Order Of Execution
2) Recursive Trigger
3) Learn about Other Trigger Framework
Recording
Episode 5 will be presented by Purushottam Bhaigade on Feb 14, 2020 at 6 PM Indian Standard Time.
Assignment
Complete below assignment to win $1000 Salesforce Voucher. Click here for rule.
| 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 |
Trigger Handler Pattern
Further Learning
Trigger Framework
Don’t forget to register for our next session on Test Classes. Check this post for all other session detail.
Please note that we have limit of 500 attendees that can join the online sessions. However, recording will be posted on our YouTube channel. 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!
13,120 total views, 60 views today
29 comments
Completed Assignment for Day 5
I have created one trigger “InvoiceAmountUpdate” and one class “InvoiceAmountUpdateHandler”
Completed Day 5 Assignment
Day 5 Assignment Completed
Episode 5 – Demystifying Apex Triggers Assignment Completed!
Completed Day 5 assignment
Day 5 Assignment is completed
completed
8 more to go
Can someone update all the solution?
completed assignment 5
Solution plz
After contest over
assignment 5 completed
Assignment 5 Completed
Day 5 Assignment is completed
Day 5 Assignment is completed
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;
}
HI bro, i have one question, you have declared empty map . since it is empty how you are searching using containskey
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!
Corrections to the code – Please check comments below
HI bro, i have one question, you have declared empty map . since it is empty how you are searching using containskey
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
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
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;
}
}
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;
}
}
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
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);
}
Keep learning