新建NSObject分类

  - (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector{
      //方法签名
      return  [NSMethodSignature signatureWithObjCTypes:"v@:"];
    }
 - (void)forwardInvocation:(NSInvocation *)anInvocation{
          NSLog(@"crash-----类：%@中 未实现该方法",NSStringFromClass([anInvocation.target             class]),NSStringFromSelector(anInvocation.selector));
    }

如下情况不会崩溃，会走消息转发机制打印信息

    UIButton *bbb = [UIButton buttonWithType:UIButtonTypeCustom];
    [bbb setTitle:@"xxxx" forState:UIControlStateNormal];
    bbb.frame = CGRectMake(100, 100, 100, 40);
    bbb.backgroundColor = [UIColor redColor];
    [self.view addSubview:bbb];
    [bbb addTarget:self action:@selector(xxxx) forControlEvents:UIControlEventTouchUpInside];

    [[NSObject new] performSelector:@selector(ffff)];