Check if CGRect null in getter
When you create an instance of your class, the _frame instance variable is automatically initialized, even before the init method is called. Since _frame is a C-struct (CGRect), its memory is cleared to all zeroes. This results in a CGRect with all zero values.
CGRectNull is a special, non-zero CGRect. So your check using CGRectIsNull() will never be true.
Using CGRectIsEmpty is a more proper check for this.
Try
- (CGRect)frame{ if (CGRectIsEmpty(_frame)) _frame = CGRectMake(0,0,60,60); return _frame;}
Here is an updated answer for Swift 4. You are able to simply use CGRect's isNull boolean property to check for CGRectNull now:
let someRect = CGRect.nullprint(someRect.isNull) // true