错误“的表达是不可转让”的timerBar.bounds.size.width分配

Question

我试图创建一个timerbar，但我得到一个错误“表达式是不可转让”的timerBar.bounds.size.width = 0

(void)viewDidLoad { 
[super viewDidLoad]; 
// Do any additional setup after loading the view, typically from a nib. 

self.view.backgroundColor = [UIColor blueColor]; 

timerBar = [[UIView alloc]initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH , 5)]; 
timerBar.backgroundColor = [UIColor whiteColor]; 
[self.view addSubview:timerBar]; 

[UIView animateWithDuration:2 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{ 
    timerBar.bounds.size.width = 0; 
} completion:^(BOOL finished) { 

}]; 

} 

我究竟做错了什么？为什么不能分配这个值？

Answer 1

你不能直接设置边界宽度为零！

CGFloat width = 0; 
timerBar.bounds = CGRectMake(0, 0, width , 5)