Use ARC Weak Reference in MRC file.

ARCWeakRef.h

//
//  ARCWeakRef.h
//  M9
//
//  Created by iwill on 2013-07-08.
//  Copyright (c) 2013年 iwill. All rights reserved.
//

#import <Foundation/Foundation.h>

/**
 *  Usage:
 *      weakifyself;
 *      [object setCallback:^{
 *          strongifyself;
 *          NSLog(@"self: %@", self);
 *      }];
 *  OR
 *      __typeof__(self) selfType;
 *      ARCWeakRef *weakRef = [ARCWeakRef weakRefWithObject:self];
 *      [object setCallback:^{
 *          __typeof__(selfType) self = weakRef.object
 *          NSLog(@"self: %@", self);
 *      }];
 */

#define weakifyself __typeof__(self) $selfType; ARCWeakRef *$weakRef = [ARCWeakRef weakRefWithObject:self]
#define strongifyself __typeof__($selfType) self = $weakRef.object

@interface ARCWeakRef : NSObject

@property (weak, nonatomic) id object;

// - (instancetype)initWithObject:(id)object;

+ (instancetype)weakRefWithObject:(id)object;

@end

ARCWeakRef.m

//
//  ARCWeakRef.m
//  M9
//
//  Created by iwill on 2013-07-08.
//  Copyright (c) 2013年 iwill. All rights reserved.
//

#import "ARCWeakRef.h"

#if ! __has_feature(objc_arc)
    // set -fobjc-arc flag: - Target > Build Phases > Compile Sources > ARCWeakRef.m + -fobjc-arc
    #error This file must be compiled with ARC. Use -fobjc-arc flag or convert project to ARC.
#endif

#if ! __has_feature(objc_arc_weak)
    #error ARCWeakRef does not support iOS 4 and lower
#endif

@implementation ARCWeakRef

- (instancetype)initWithObject:(id)object {
    self = [super init];
    if (self) {
        self.object = object;
    }
    return self;
}

+ (instancetype)weakRefWithObject:(id)object {
    return [[self alloc] initWithObject:object];
}

@end