Create rollup summary using Apex trigger on custom object

Hey guys, today in this post we are going to learn about How to create roll-up summary trigger for count child records on custom object using Apex trigger in Salesforce.
parentObjTrigger:- Custom Fields & Relationships
Create a custom field on parent Object name as childRollUp__c (Number Type).
childObjTrigger:- Custom Fields & Relationships
Create a lookup relationship field on child Object name as childLookup__c : Lookup(parentObjTrigger).
Real time scenarios:- Write a roll-up summary trigger for count child records on custom parent object.
Create a custom field (Number Type) on parent object, calculate the total number of related child records and put into them.
Files we used in this post example:-
childObjTriggerRollUp.apxt
Apex Class Trigger
It will be fired whenever insert, update and delete a record on child object
Parent Cusotm Object:- parentObjTrigger__c
Custom Field :- childRollUp__c
Parent Object with Custom Field
Trigger on child object and calculate the total numberof related child records on the parent object.
Child Custom Object:- childObjTrigger__c
Custom Field:- childLookup__c >> Lookup(parentObjTrigger)
Child Object with Field
childLookup__c : Lookup(parentObjTrigger) field it is help to communicate on parent object.
You can download file directly from github by click here
Final Output

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Step 1:- Apex Class Trigger : childObjTriggerRollUp.apxt
From Developer Console >> File >> New >> Apex Trigger
childObjTriggerRollUp.apxt [Apex Class Trigger]
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Originally published at https://www.w3web.net on August 8, 2020.