- #if __has_feature(arr)
- # if __IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_5_0
- # define block_unretained(obj) id _block_##obj __weak = (obj)
- # else
- # define block_unretained(obj) id _block_##obj __unsafe_unretained = (obj)
- #else
- # define block_unretained(obj) id _block_##obj __block = (obj)
- #endif