renebigot/MBProgressHUD — comment on commit a3be7e5d7f362b22437b257130cb14592ad564c6
File:  line 0
By jerbeers:

You can drop the iVar declaration and use this for the property declaration:

#if __has_feature(objc_arc_weak)
@property (weak) id delegate;
#elif __has_feature(objc_arc)
@property (unsafe_unretained) id delegate;
#else
@property (assign) id delegate;
#endif

Then you can keep the zeroing weak references feature for iOS5 and compatibility with iOS4