BLOCK 死循环

__weak typeof(self) weakSelf = self;

myObj.myBlock =  ^{

    __strong typeof(self) strongSelf = weakSelf;

    if (strongSelf) {

      [strongSelf doSomething]; // strongSelf != nil

      // preemption, strongSelf still not nil

      [strongSelf doSomethingElse]; // strongSelf != nil

    }

    else {

        // Probably nothing...

        return;

         

    }

};

 

block中需要对weakSelf进行strong,保证代码在执行到block中，self不会被释放，当block执行完后，会自动释放该strongSelf