weak:

/*!

Creates a __weak version of the variable provided,

which can later be safely used or converted into strong variable via @strongify.

*/

#define weakify(var) \

try {} @catch (...) {} \

__weak __typeof__(var) var ## _weak = var;

strong:

/*!

Creates a strong shadow reference of the variable provided.

Variable must have previously been passed to @weakify.

*/

#define strongify(var) \

try {} @catch (...) {} \

__strong __typeof__(var) var = var ## _weak;