在iOS7和iOS8中不同的自动布局下转换UILabel

Question

我想旋转uilabel，在iOS7和iOS8中似乎有所不同。任何人都可以解释原因吗？

这是我的演示代码，使用pureLayout设置autolayout：

UIView *view = [UIView newAutoLayoutView];
[self.view addSubview:view];
[view autoPinEdgeToSuperviewEdge:ALEdgeTop withInset:20];
[view autoAlignAxisToSuperviewAxis:ALAxisVertical];
[view autoSetDimensionsToSize:CGSizeMake(20, 100)];
view.backgroundColor = [UIColor lightGrayColor];

UILabel *topLabel = [UILabel newAutoLayoutView];
[view addSubview:topLabel];
topLabel.backgroundColor = [UIColor redColor];
topLabel.text = @"The top label text";
[topLabel autoPinEdgesToSuperviewEdgesWithInsets:UIEdgeInsetsZero excludingEdge:ALEdgeBottom];

CGAffineTransform tran = CGAffineTransformMakeRotation(-M_PI_2);
topLabel.transform = tran;

和topLabel的框架：

iOS8:{{-1.25, 1.25}, {22.5, 20}}
iOS7:{{0, 0}, {20, 135}}

iOS7的结果是我想要的。当我使用IB进行自动布局时，同样的结果

Answer 1

人们似乎认为它与iOS 7和8中的约束行为有关。Animation of CGAffineTransform in iOS8 looks different than in iOS7