apex_task_campaignMemberStatus_change.apex

trigger newTask on CampaignMember (after insert, after update)  { 
  
  Set<String> leadIds = new Set<String>();
  Set<String> campaignIds = new Set<String>();

  for(CampaignMember cm : Trigger.new) { 
  	  if(cm.LeadId!=null) leadIds.add(cm.LeadId);
  	  campaignIds.add(cm.CampaignId);
  }

  Map<String, Lead> leadMap = new Map<String, Lead>();
  for(Lead l : [Select Id 
				From Lead
				Where Id IN :leadIds]) {
  	  leadMap.put(l.Id, l);
  }
  
  Map<String, Campaign> campMap = new Map<String, Campaign>();
  for(Campaign c : [Select Id, Type, Name, Parent.name from Campaign where Id IN:campaignIds]) {
      campMap.put(c.Id, c);
  }
  
  List<Task> tasksToInsert = new List<Task>();
  for(CampaignMember cm : Trigger.new) {
  	  if(cm.LeadId!=null) { 
	      Lead l = leadMap.get(cm.LeadId);
	      Campaign cmp = campMap.get(cm.CampaignId);
      
          String campaignInfoString = cmp.type + '-' + cmp.name + '-' + l.Status;
          Task t = new Task();
          t.OwnerId = UserInfo.getUserId();
          t.Subject = campaignInfoString;
          t.Status = 'Completed';
          t.Priority = 'Normal';
          t.WhatId = l.Id;
          tasksToInsert.add(t);
  	  }
  }
  insert tasksToInsert;
  
}