create field on opportunity and check for increment value

## > Create a field on Opportunity Line item(Serial No (Text)) and populate increment values once an Opportunity Line Item is added. Let’s say if we add 3 products then the sequence would be “1,2,3”. Now if we delete 2 and again add one more product this must be 4 irrespective of the deleted sequence number.




 Trigger oppLineItemCountTrigger on Opportunity (After Insert , After Update){
  switch on Trigger.OperationType{
    when AFTER_INSERT{
      oppLineItemCountHelper.lineItemCheck(Trigger.new);
    }
    when AFTER_UPDATE{
    oppLineItemCountHelper.lineItemCheck(Trigger.new);
    }
  }
 }


 Public with sharing class oppLineItemCountHelper{
  public static void lineItemCheck(List<Opportunity> oppList){
      if(oppList.size() > 0){
        Set<Opportunity> oppSet = new Set();
        for(Opportunity opp: oppList){
        oppSet.add(opp.Id);
        }
       List<Opportunity> oppUpdated = new List<Opportunity>();
       List<Opportunity> oppData = [SELECT Id, firstName, LastName, Ammount, StageName, Serial_No__c from Opportunity where Id =: oppSet];
       for(Opportunity oppObj : oppData){
        for(int i=0; i < oppList.size() ; i++){
          oppObj.Serial_No__c = i;
        }
        oppUpdated.add(oppObj);
       }
       if(oppUpdated.size()> 0){
       INSERT oppUpdated;
       }
      }
    }
 }