WeakSelf StrongSelf的宏写法

在YYKit中看到这样的宏

#ifndef weakify
#if DEBUG
#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
#else
#if __has_feature(objc_arc)
#define weakify(object) try{} @finally{} {} __weak __typeof__(object) weak##_##object = object;
#else
#define weakify(object) try{} @finally{} {} __block __typeof__(object) block##_##object = object;
#endif
#endif
#endif

#ifndef strongify
#if DEBUG
#if __has_feature(objc_arc)
#define strongify(object) autoreleasepool{} __typeof__(object) object = weak##_##object;
#else
#define strongify(object) autoreleasepool{} __typeof__(object) object = block##_##object;
#endif
#else
#if __has_feature(objc_arc)
#define strongify(object) try{} @finally{} __typeof__(object) object = weak##_##object;
#else
#define strongify(object) try{} @finally{} __typeof__(object) object = block##_##object;
#endif
#endif
#endif

然后在处理block循环引用的时候就可以这样

   MyObject *obj = [[MyObject alloc] init];
    self.myObj = obj;
    @weakify(self)
    self.myObj.test = ^(){
        @strongify(self)
        self.mLabel.text = @"aaa";
    };

这样使用非常方便，在block中依然可以用self
但是目前尚未读懂这个宏。。希望知道的留个言。弄清楚之后也会更新此博客。
比如

//weakify
try{} @finally{} {} __weak __typeof__(object) weak##_##object = object;
//strongify
autoreleasepool{} __typeof__(object) object = weak##_##object;

这里面try{} @finally{} {}是什么作用？不会是只为了让前面多个@？我试着把try{} @finally{} {}去掉，autoreleasepool{}去掉,依然可以正常使用。这两句是干什么的？