What's the difference between -existingObjectWithID:error: and –objectWithID:?

Question

What's the difference between -existingObjectWithID:error: and –objectWithID: ?

Answer 1

objectWithID: assumes the object exists so if you give it a bad ID it will throw an exception when you attempt to access a property on the returned entity. Also, this method always returns an entity.

existingObjectWithID:error: will return an object if it exists and nil if it does not. If there was an error it will populate the error pointer.