让左边对象集合中的元素执行同一个方法
makeObjectsPerformSelector:让左边对象集合中的元素执行makeObjectsPerformSelector这个方法
[self.answerView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
makeObjectsPerformSelector:让左边对象集合中的元素执行makeObjectsPerformSelector这个方法
[self.answerView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];