I am confused about using a Before or After Update trigger. The scenario is that I want to create a new task and relate it to an opportunity when it's updated with a Stage = 'Closed Won'.

From what I've read so far, you always need to use After Update trigger in such cases. But what if I use a before update trigger? I do have the opp Id in the database and I can use it to associate it to the newly created task. When the opp is saved , the task will be created as well. Am I missing something here in my logic?

I am confused about using a Before or After Update trigger. The scenario is that I want to create a new task and relate it to an opportunity when it's updated with a Stage = 'Closed Won'.

From what I've read so far, you always need to use After Update trigger in such cases. But what if I use a before update trigger? I do have the opp Id in the database and I can use it to associate it to the newly created task. When the opp is saved , the task will be created as well. Am I missing something here in my logic?

trigger ClosedOpportunityTrigger on Opportunity (after insert, before update) {
    
//Create a list to hold all opportunities for which tasks need to be created
List<Opportunity> oppList = new List<Opportunity>();

for(Opportunity opp: Trigger.new) {
    
    if(Trigger.isInsert)    {
        if(opp.StageName=='Closed Won') {
            oppList.add(opp);
        }
    }
    
       //Make sure trigger only works on updated Opportunities 
       where old value != new value
       else {
        
        Opportunity oldOpp  = Trigger.oldMap.get(opp.Id);
        Boolean oldOppIsWon = oldOpp.StageName.equals('Closed Won');
        Boolean newOppIsWon = opp.StageName.equals('Closed Won');
        
        if(!oldOppIsWon && newOppIsWon) {
            
            oppList.add(opp);
        }
    }
    
  }

List<Task> taskList = new List<Task>();
for(Opportunity opp :oppList) {
    
    Task t        = new Task();
    t.WhatId      = opp.Id;
    t.Subject     = 'Follow up test task';
    t.Priority    = 'Normal';
    t.Status      = 'Not Started';
    taskList.add(t);
}

insert taskList;
     
}