Question

My goal is to be able to update objects in NSUserDefaults.

This is my approach, and my concern is that when I replace the arrays using removeObjectForKey, is there any memory issue than can be created. The objects that were in the array are saved in objectArray by means of initWithArray:. oldSavedArray is the array with the previous contents of NSUserDefaults.

objectArray = [[NSMutableArray alloc] initWithArray:oldSavedArray];

if ([objectArray containsObject:myObject]){

            // remove the current object
            [objectArray removeObject:_currentFood];

            // reset our new array of objects
            [_defaults removeObjectForKey:@"mySavedData"];
            [_defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:objectArray] forKey:@"mySavedData"];
        }
        else{ 

            // add the current object
            [objectArray addObject:_currentFood];                

            // reset our new array of favorite food
            [_defaults removeObjectForKey:@"mySavedData"];
            [_defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:objectArray] forKey:@"mySaveData"];
        }

Answer 1

To answer your question

Is there any memory issue by using “removeObjectForKey”?.

My answer is No. But that step is not necessary.

[defaults setObject:forKey:]

is enough.