Null value in trigger.new context variable

Question

I have a simple trigger that updates lead address filed from another custom object. When I am trying to add lead id in set variable, the following error is thrown:

argument cannot be null exception

Snippet code:

Trigger trigger_name on lead (before insert){
    Set<id> setid = new set<id>();
    For(lead of : trigger.new )
    {
        setid.add(of.id);
    }
}

Answer 1

As @Samir said, the id field is not available in a before insert trigger because Id's are available after insert.

Also, there's a problem with your code. That's not how you instantiate a Set of Id's.

Here's the right code:

   Trigger yourTriggerName on lead (after insert){
       Set<Id> leadSet = new Set<Id>();
       for(Lead lead : Trigger.new)
       {
          leadSet.add(lead.id);
       }
   }

Answer 2

In before insert trigger,id is not available as the record is not yet inserted,To get the id, change your trigger definition to -

Trigger triggerName on lead (after insert)