RSWeakifySelf.h

/**
 * Several macros simplifying use of weak references to self inside blocks
 * which goal is to reduce risk of retain cycles.
 *
 * Version 2. Uses GCC statement expressions 
 * instead of capturing self via block closure.
 *
 * Example:
 * @code
 
 @interface Example : NSObject{
    int _i;
 }
 @property (nonatomic,copy) void(^block)(void);
 @end
 
 @implementation Example
 -(void)someMethod{
    self.block = weakifySelf(^{
        // Self may be nil here
        [self doSomeWork];
        strongifyAndReturnIfNil(self);
        // Self is strong and not nil.
        // We can do ivars dereferencing
        // and other stuff safely
        self->_i = 42;
    });
 }
 @end
 
 * @endcode
 */

/**
 * Takes a block of any signature as an argument
 * and makes all references to self in it weak.
 */
#define weakifySelf(BLOCK) ({ \
    _Pragma("clang diagnostic push") \
    _Pragma("clang diagnostic ignored \"-Wshadow\"") \
    id __weak _weak_self = self; \
    __typeof(self) __weak self = _weak_self; \
    BLOCK; \
    _Pragma("clang diagnostic pop") \
})

/**
 * Creates a strong reference to a variable
 * that will shadow the original
 */
#define strongify(VAR) \
    id _strong_##VAR = VAR; \
    __typeof(VAR) __strong VAR = _strong_##VAR;

/**
 * Creates a strong reference to a variable and returns if it is nil
 */
#define strongifyAndReturnIfNil(VAR) \
    strongify(VAR) \
    if (!(VAR)){ return;}