iOS编程中的Block循环引用解决

#ifndef BlockCycle_h
#define BlockCycle_h

#warning 这是一个MRC/ARC通用的weakify和strongify
/**
 * 强弱引用转换，用于解决代码块（block）与强引用self之间的循环引用问题
 * 调用方式: `@weakify_self`实现弱引用转换，`@strongify_self`实现强引用转换
 *
 * 示例：
 * @weakify_self
 * [obj block:^{
 * @strongify_self
 * self.property = something;
 * }];
 */
#ifndef    weakify_self
#if __has_feature(objc_arc)
#define weakify_self autoreleasepool{} __weak __typeof__(self) weakSelf = self;
#else
#define weakify_self autoreleasepool{} __block __typeof__(self) blockSelf = self;
#endif
#endif

#ifndef    strongify_self
#if __has_feature(objc_arc)
#define strongify_self try{} @finally{} __typeof__(weakSelf) self = weakSelf;
#else
#define strongify_self try{} @finally{} __typeof__(blockSelf) self = blockSelf;
#endif
#endif
/**
 * 强弱引用转换，用于解决代码块（block）与强引用对象之间的循环引用问题
 * 调用方式: `@weakify(object)`实现弱引用转换，`@strongify(object)`实现强引用转换
 *
 * 示例：
 * @weakify(object)
 * [obj block:^{
 * @strongify(object)
 * strong_object = something;
 * }];
 */
#ifndef    weakify
#if __has_feature(objc_arc)
#define weakify(object) autoreleasepool{} __weak __typeof__(object) weak##_##object = object;
#else
#define weakify(object) autoreleasepool{} __block __typeof__(object) block##_##object = object;
#endif
#endif
#ifndef    strongify
#if __has_feature(objc_arc)
#define strongify(object) try{} @finally{} __typeof__(object) strong##_##object = weak##_##object;
#else
#define strongify(object) try{} @finally{} __typeof__(object) strong##_##object = block##_##object;
#endif
#endif

#endif /* BlockCycle_h */