一、基础

weak

NSObject*  a = [NSObject new];
    
   __weak typeof(a)wea = a;
    
    NSObject* c = wea;
    
    self.aa = ^{
        
        NSLog(@"%@  %@",wea,c);
    };

在这个里面，c = wea，其实等价于__strong NSObject *c = wea;