Week 3

Lead trigger

trigger LeadTrigger on Lead (after insert, after update)
{
    if(Trigger.isAfter)
    {
        if(trigger.isInsert)
        {
             LeadHandlerClass.CreateTask(Trigger.New,Null);
        }
        if(Trigger.isUpdate) 
        {
            LeadHandlerClass.CreateTask(Trigger.New,Trigger.oldMap);  
        } 
        
    }
}

LeadHandlerClass

public class LeadHandlerClass
{
    
    
       Public Static Void CreateTask(List<Lead> Listofleads, Map <Id, Lead> OldLeadMap)
        {
            
            
              List<Task> newlistoftasks = new List<Task>();
        
              for(Lead ld : Listofleads)
               {
                      if(  ld.ProductInterest__c !=null && (OldLeadMap == null || ld.ProductInterest__c != OldLeadMap.get(ld.id).ProductInterest__c))
                           {
                             Task t = new Task();
                               t.Subject = 'Follow With New Lead';
                               t.Status = 'Not Started';
                               t.WhoId = ld.Id;
                               newlistoftasks.add(t);
                           }
                      
                If(!newlistoftasks.isEmpty())
                     {
                        insert newlistoftasks;
                     }
               }   

          }
}