masonry 设置圆角时机

问题：设置完约束之后是无法立刻获取frame的

解决：layoutSubviews 视图布局完成之后，此时试图的大小都已经获取到了，在设置

代码：如下

- (void)layoutSubviews{
    [super layoutSubviews];
    self.showEmitterView.layer.cornerRadius = self.showEmitterView.width/2;
    self.showCountLabel.layer.cornerRadius = self.showCountLabel.width/2;
    self.showEmitterView.risingY = self.showCountLabel.height/2;
}

那么问题来了～如果再controller中呢～如何获取view的frame

解决：看uikit中uiviewcontroller中这一段代码～（看注释）

// Called just before the view controller's view's layoutSubviews method is invoked. Subclasses can implement as necessary. The default is a nop.
- (void)viewWillLayoutSubviews NS_AVAILABLE_IOS(5_0);
// Called just after the view controller's view's layoutSubviews method is invoked. Subclasses can implement as necessary. The default is a nop.
- (void)viewDidLayoutSubviews NS_AVAILABLE_IOS(5_0);

意思就是：重写viewDidLayoutSubviews吧，这个方法能获取到～

- (void)viewDidLayoutSubviews{
    [super viewDidLayoutSubviews];
    self.showEmitterView.layer.cornerRadius = self.showEmitterView.width/2;
    self.showCountLabel.layer.cornerRadius = self.showCountLabel.width/2;
    self.showEmitterView.risingY = self.showCountLabel.height/2;
}