Apex trigger to create and count the number of child records associated with parent object based on custom field when parent record is created/updated in Salesforce | Count the number of child record using trigger in Salesforce

Q: How do you handle errors in Apex class?

Apex uses the try, catch, and finally block to handle an exception. You “try” to run your code and if an exception occurs you catch it and write the code to handle it in the “catch” block. You write the code that must execute whether an exception occurs or not in the final block.

Q: How do I run an Apex class in developer console?

Follow the steps to execute apex code in developer console. Now go to Debug=>Open execute anonymous window. Use CTRL + E shortcut to open window to execute apex code. Now click on execute button.

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Hey guys, today in this post we are going to learn about Apex trigger to create and count the number of child records associated with parent object based on custom field when parent record is created/updated in Salesforce.

Real time scenarios:- Write a trigger on parent object where create a custom field as Employee (Number type).

If user insert the parent record, the child record should be automatic inserted equal to the same value of employee.

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Or if user update the value of employee less then the total number of child records, in this case the child records should be exist only equal to value of employee size, rest records of child object should be automatic removed.

Don’t forget to check out:- Create a Apex Trigger on Account to Update the Associated Contact Account Name Null Whenever Account Record is Updated in Salesforce Click Here For More Information

Files we used in this post example

EmployeeSizeTrigger2.apxt

Apex Class Trigger

It will be fired whenever insert or update a record on parent object

Parent Cusotm Object:- parentObjTrigger__c

Custom Field:- EmployeeName__c

Parent Object with Custom Field

Trigger on parent object and updae the count of related child records with the custom field value of parent object.

Child Custom Object:- childObjTrigger__c

Custom Field:- childLookup__c : Lookup(parentObjTrigger)

Child Object with Custom Field

childLookup__c : Lookup(parentObjTrigger) field it is help to communicate on parent object.

Live Example

Other related post that would you like to learn in Salesforce

Step 1:- Apex Class Trigger : EmployeeSizeTrigger2.apxt

From Developer Console >> File >> New >> Apex Trigger

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EmployeeSizeTrigger2.apxt [Apex Class Trigger]

   trigger EmployeeSizeTrigger2 on parentObjTrigger__c (before insert, before update, after insert, after update, before delete, after delete) {  
    List<parentObjTrigger__c> prntList= new List<parentObjTrigger__c>();
    Set<Id> setOldId= new Set<Id>(); 
    List<childObjTrigger__c> childListNew= new List<childObjTrigger__c>();
    List<childObjTrigger__c> childList= new List<childObjTrigger__c>();
    Set<Id> childSetId = new Set<Id>();
    if(trigger.isBefore){
        system.debug('Event before trigger');
        if(trigger.isDelete){
            prntList=trigger.old;
            prntList = [Select Id, Name, Status__c, LastModifiedDate__c, (Select Id, Status__c, LastModifiedDate From childObjTriggers__r) From parentObjTrigger__c Where Id=:trigger.old];
            system.debug('prntListOld' + prntList);
            for(parentObjTrigger__c oldList: prntList){               
                for(childObjTrigger__c childList: oldList.childObjTriggers__r){
                    system.debug('childList ' + childList);
                    setOldId.add(childList.Id);
                }
            }
            system.debug('setOldId## ' + setOldId ); 
            List<childObjTrigger__c> childId=[Select Id, Name From childObjTrigger__c Where Id IN:setOldId];
            delete childId;
        }
    }else if(trigger.isAfter){
        system.debug('Event after trigger');
        decimal empVal;
        if(trigger.isDelete){
            system.debug('setOldId## ' + setOldId ); 
            
        }
        else if(trigger.isInsert){
            prntList=trigger.new;
            
            for(parentObjTrigger__c prntNew:prntList){
                empVal = prntNew.Employee__c;
            }
            for(Integer i=0; i<empVal; i++){
                for(parentObjTrigger__c newRow:prntList){
                    childObjTrigger__c childItem = new childObjTrigger__c();
                    childItem.EmployeeName__c='Employee Name ' + i;
                    childItem.childLookup__c= newRow.Id; 
                    childList.add(childItem);
                }
                
            } 
            
            insert childList; 
        }
        else if(trigger.isUpdate){
            prntList=trigger.new;
            system.debug('trigger is updated');
             List<childObjTrigger__c> childObjRelList = [Select Id, Status__c, LastModifiedDate From childObjTrigger__c Where childLookup__c=:prntList[0].Id]; 
            
            for(parentObjTrigger__c prntNew:prntList){
                empVal = prntNew.Employee__c;
            }
           
            for(parentObjTrigger__c updatePtr:prntList){
                for(childObjTrigger__c childItemRel:childObjRelList){
                    system.debug('childItemRel ' + childItemRel);
                    
                    childSetId.add(childItemRel.Id); 
                } 
            }
            system.debug('empVal Before ' + empVal);
            if(empVal > childSetId.size()){
                empVal = empVal-childSetId.size();
                system.debug('empVal After ' + empVal);
                for(Integer i=0; i<empVal; i++){
                    system.debug('empValAA ' + empVal + i);
                    for(parentObjTrigger__c updatePtr2:prntList){
                        childObjTrigger__c childItem2 = new childObjTrigger__c();
                        childItem2.EmployeeName__c='childSetEmp ' + i;
                        childItem2.childLookup__c= updatePtr2.Id;
                        childListNew.add(childItem2);
                    } 
                }
                system.debug('childListNew 2# ' + childListNew );
                upsert childListNew;
                
            }else{
                Set<Id> resId = new Set<Id>();
                system.debug('empVal$$ ' + empVal);
                List<childObjTrigger__c> childObj = new List<childObjTrigger__c>(); 
                List<childObjTrigger__c> childObjNullVal = new List<childObjTrigger__c>();
                for(parentObjTrigger__c parentRelList:prntList){
                    for(childObjTrigger__c childItemRel:childObjRelList){
                        system.debug('childItemRel1 ' + childItemRel);                                             
                        resId.add(childItemRel.Id);
                        childObj.add(childItemRel);
                    }
                    
                }
                
                empVal = resId.size() - empVal;
                system.debug('empVal New val ' + empVal);
                
                for(Integer i=0; i<empVal; i++){
                    system.debug('empVal Loop Val ' + i);
                      childObj[i].childLookup__c=null;
                      childObjNullVal.add(childObj[i]);
                }
               update childObjNullVal;
               system.debug('childObjNullVal ' + childObjNullVal); 
                
                system.debug('childObj # ' + childObj);
                system.debug('resId #1 ' + resId);
                system.debug('childObj$ ' + childObj);
                
            }
            
            
        }
        
    }
}

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trigger EmployeeSizeTrigger2 on parentObjTrigger__c (before insert, before update, after insert, after update, before delete, after delete) {

List<parentObjTrigger__c> prntList= new List<parentObjTrigger__c>();

Set<Id> setOldId= new Set<Id>();

List<childObjTrigger__c> childListNew= new List<childObjTrigger__c>();

List<childObjTrigger__c> childList= new List<childObjTrigger__c>();

Set<Id> childSetId = new Set<Id>();

if(trigger.isBefore){

system.debug('Event before trigger');

if(trigger.isDelete){

prntList=trigger.old;

prntList = [Select Id, Name, Status__c, LastModifiedDate__c, (Select Id, Status__c, LastModifiedDate From childObjTriggers__r) From parentObjTrigger__c Where Id=:trigger.old];

system.debug('prntListOld' + prntList);

for(parentObjTrigger__c oldList: prntList){

for(childObjTrigger__c childList: oldList.childObjTriggers__r){

system.debug('childList ' + childList);

setOldId.add(childList.Id);

}

system.debug('setOldId## ' + setOldId );

List<childObjTrigger__c> childId=[Select Id, Name From childObjTrigger__c Where Id IN:setOldId];

delete childId;

}

}else if(trigger.isAfter){

system.debug('Event after trigger');

decimal empVal;

if(trigger.isDelete){

system.debug('setOldId## ' + setOldId );

}

else if(trigger.isInsert){

prntList=trigger.new;

for(parentObjTrigger__c prntNew:prntList){

empVal = prntNew.Employee__c;

}

for(Integer i=0; i<empVal; i++){

for(parentObjTrigger__c newRow:prntList){

childObjTrigger__c childItem = new childObjTrigger__c();

childItem.EmployeeName__c='Employee Name ' + i;

childItem.childLookup__c= newRow.Id;

childList.add(childItem);

}

insert childList;

}

else if(trigger.isUpdate){

prntList=trigger.new;

system.debug('trigger is updated');

List<childObjTrigger__c> childObjRelList = [Select Id, Status__c, LastModifiedDate From childObjTrigger__c Where childLookup__c=:prntList[0].Id];

for(parentObjTrigger__c prntNew:prntList){

empVal = prntNew.Employee__c;

}

for(parentObjTrigger__c updatePtr:prntList){

for(childObjTrigger__c childItemRel:childObjRelList){

system.debug('childItemRel ' + childItemRel);

childSetId.add(childItemRel.Id);

}

system.debug('empVal Before ' + empVal);

if(empVal > childSetId.size()){

empVal = empVal-childSetId.size();

system.debug('empVal After ' + empVal);

for(Integer i=0; i<empVal; i++){

system.debug('empValAA ' + empVal + i);

for(parentObjTrigger__c updatePtr2:prntList){

childObjTrigger__c childItem2 = new childObjTrigger__c();

childItem2.EmployeeName__c='childSetEmp ' + i;

childItem2.childLookup__c= updatePtr2.Id;

childListNew.add(childItem2);

}

system.debug('childListNew 2# ' + childListNew );

upsert childListNew;

}else{

Set<Id> resId = new Set<Id>();

system.debug('empVal$$ ' + empVal);

List<childObjTrigger__c> childObj = new List<childObjTrigger__c>();

List<childObjTrigger__c> childObjNullVal = new List<childObjTrigger__c>();

for(parentObjTrigger__c parentRelList:prntList){

for(childObjTrigger__c childItemRel:childObjRelList){

system.debug('childItemRel1 ' + childItemRel);

resId.add(childItemRel.Id);

childObj.add(childItemRel);

}

empVal = resId.size() - empVal;

system.debug('empVal New val ' + empVal);

for(Integer i=0; i<empVal; i++){

system.debug('empVal Loop Val ' + i);

childObj[i].childLookup__c=null;

childObjNullVal.add(childObj[i]);

}

update childObjNullVal;

system.debug('childObjNullVal ' + childObjNullVal);

system.debug('childObj # ' + childObj);

system.debug('resId #1 ' + resId);

system.debug('childObj$ ' + childObj);

}

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FAQ (Frequently Asked Questions)

How do you handle errors in Apex class?

Apex uses the try, catch, and finally block to handle an exception. You “try” to run your code and if an exception occurs you catch it and write the code to handle it in the “catch” block. You write the code that must execute whether an exception occurs or not in the final block.

How do I run an Apex class in developer console?

Follow the steps to execute apex code in developer console. Now go to Debug=>Open execute anonymous window. Use CTRL + E shortcut to open window to execute apex code. Now click on execute button.

What is Apex test class in Salesforce?

The Apex testing framework enables you to write and execute tests for your Apex classes and triggers on the Lightning Platform. Apex unit tests ensure high quality for your Apex code and let you meet requirements for deploying Apex.

Author of w3web.net

Hi, This is Vijay Kumar behind the admin and founder of w3web.net. I am a senior software developer and working in MNC company from more than 8 years. I am great fan of technology, configuration, customization & development. Apart of this, I love to write about Blogging in spare time, Working on Mobile & Web application development, Salesforce lightning, Salesforce LWC and Salesforce Integration development in full time. [Read full bio] | | The Sitemap where you can find all published post on w3web.net

5 thoughts on “Apex trigger to create and count the number of child records associated with parent object based on custom field when parent record is created/updated in Salesforce | Count the number of child record using trigger in Salesforce”

Mohan Manjhi

January 17, 2021 at 3:17 am

A thankful and good information by you thanks for this info.
Tarachand Khyalia

February 1, 2021 at 10:28 am

helpful info share…. great
Anmolk

March 10, 2021 at 6:28 pm

hello dear you write very good blog posts. Your grateful anmolk.
alex

April 29, 2021 at 9:38 am

helpful info share…. great…
Fiona Xu

August 9, 2021 at 5:38 am

Amazing article, and I have learnt a lot

Apex trigger to create and count the number of child records associated with parent object based on custom field when parent record is created/updated in Salesforce | Count the number of child record using trigger in Salesforce

Files we used in this post example

EmployeeSizeTrigger2.apxt [Apex Class Trigger]

How do you handle errors in Apex class?

How do I run an Apex class in developer console?

What is Apex test class in Salesforce?

Related Topics | You May Also Like

Author of w3web.net

5 thoughts on “Apex trigger to create and count the number of child records associated with parent object based on custom field when parent record is created/updated in Salesforce | Count the number of child record using trigger in Salesforce”

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