Old and New Values of Parent fields with Re-parenting on Child Trigger

Question

I know we have to query the parent fields to access them on the child object trigger. How can I get the old and new values of the parent fields when its parent record has been changed. I have two objects.

• Case (Child of Look-up to WebID Object)
• WebID

I need to access old and new value of the Status__c custom field on WebID__c whenever Case gets its parent WebID Changed. Any inputs on the single line logic to retrieve the old and new values of parent field WebID__r.Status__c?

Thanks in Advance!

Answer 1

I would recommend creating a map of WebIDs to it's Status by querying the WebID object after creating a set from the old and new ids using the WebID__c field from the old/new child records. Then you can use that map to access the status of the WebID record based on the ID of the old record vs the new record.

Answer 2

From the above @JennyB answer, here is the code below.

trigger caseTrigger on Case(before update)
{
  set<Id> newSet = new set<Id>(); 
  set<Id> oldSet = new set<Id>();
  for(Case cs:Trigger.New)
  {
     newSet.add(cs.WebID__c);
  }
  for(Case cs:Trigger.Old)
  {
     oldSet.add(cs.WebID__c);
  }
  map<Id, WebID__c> allWebIdMap = new map<Id, WebID__c>(
                    [select Id, Status__c from WebID__c where Id IN: newSet 
                    or Id IN:oldSet]);
  map<Id, WebID__c> newWebIDMap = new map<Id, WebID__c>();
  map<Id, WebID__c> oldWebIDMap = new map<Id, WebID__c>();

  for(Id WebIDId : allWebIDMap.keySet()) 
  {
      WebID__c currentWebID = allWebIDMap.get(WebIDId);
     if(newSet.contains(WebIDId)) 
     { 
          newWebIDMap.put(WebIDId, currentWebID); 
     }
     if(oldSet.contains(WebIDId)) 
     { 
          oldWebIDMap.put(WebIDId, currentWebID); 
     }
  }

  for(Case c:Trigger.New)
  {
     String oldStatus = oldWebIDMap.get(Trigger.oldMap.get(c.Id).WebID__c).Status__c;
     String newStatus = newWebIDMap.get(c.WebID__c).Status__c;
     system.debug('---------oldStatus----------'+oldStatus);
     system.debug('---------newStatus----------'+newStatus); 
     // perform required operation here  

  }
}