［object-c]像java一样优雅的写回调

    void (^block)(NSString *cmd, NSDictionary *retDict) = ^(NSString *cmd, NSDictionary *retDict){        NSLog(@"%@, %@", cmd, retDict);    };    int cmd = 3;    NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithObjectsAndKeys:block, @"3", nil];        void (^block2)(NSString *cmd, NSDictionary *retDict) = [dict valueForKey:@"3"];    block2(@"100", [NSDictionary dictionaryWithObjectsAndKeys:@"1", @"1", nil]);