What is a good way of guarding against NPEs while recalling attributes of objects in lists?

Question

An as example, say I have a trigger (list object) with accounts in it, and I want to compare the "Status" attribute of an account to a String. This is how I do it right now:

if (trigger.oldMap.get(account.id).Status__c != null && trigger.oldMap.get(account.id).Status__c.contains('active')) {}

My true purpose is simply to execute the second expression, but in the case that the current account did not have a Status, I would be returned a NPE because of the compareTo call. So I add in a not null check first which seems like a terribly inefficient way of doing things.

How can this be done better?

Answer 1

You could use isNotBlank or isNotEmpty instead (though I guess it amounts to the same as a null check)

if ( String.isNotBlank(trigger.oldMap.get(account.id).Status__c) &&  trigger.oldMap.get(account.id).Status__c.contains('active') ) {}

According to the docs, isNotBlank Returns true if the specified String is not whitespace, not empty (''), and not null; otherwise, returns false.

To code defensively you will have to do some kind of check, whether it be null checking or isBlank/isEmpty etc. if there is a chance that Status__c could be null.

What you could do is write your own static method to check and return '' if null? e.g.

static String makeNullString( String in ) {
  return in == null ? '' : in;
}

Then you could do this instead:

if (makeNullString(trigger.oldMap.get(account.id).Status__c).contains('active')) {}