I understand the ARC release notes, but I was wondering what that means and what the system classes are:
You can implement the dealloc method if you need to manage resources other than freeing instance variables. You do not need (indeed, you cannot) free instance variables, but you may need to call [systemClassInstance setDelegate:nil]other classes that are not compiled using ARC for system classes.
[systemClassInstance setDelegate:nil]
This is right here. ARC Release Notes According to New ARC Rules
What are the so-called system classes?
, , "NS" "UI". Apple , ARC. ARC , .
, (, UIApplication) - (nonatomic, assign) (nonatomic, weak). , , . , assign unsafe_unretained ARC. , dealloc. , , .
(nonatomic, assign)
(nonatomic, weak)
assign
unsafe_unretained