我的问题是当我尝试呈现样式ActionSheet的UIAlertController时.
这是我的代码：

UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Title"
                                                               message:@"My message"
                                                        preferredStyle:UIAlertControllerStyleActionSheet];

UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:nil];
[alert addAction:cancelAction];

UIAlertAction *OKAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:nil];
[alert addAction:OKAction];

UIAlertAction *destroyAction = [UIAlertAction actionWithTitle:@"Destroy" style:UIAlertActionStyleDestructive handler:nil];
[alert addAction:destroyAction];

UIPopoverPresentationController *popPresenter = [alert popoverPresentationController];
popPresenter.sourceView = self.view;
popPresenter.sourceRect = self.view.bounds;

[self presentViewController:alert animated:YES completion:nil];

这是错误：

Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you 
don't want. Try this: 
(1) look at each constraint and try to figure out which you don't expect; 
(2) find the code that added the unwanted constraint or constraints and fix it. 
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand,refer to the documentation for the UIView property 
translatesAutoresizingMaskIntoConstraints) 
(
    "<NSLayoutConstraint:0x7c00ab40 H:[UIView:0x7c0764c0(304)]>","<NSLayoutConstraint:0x7b6c7f80 _UIAlertControllerView:0x7b6c2e50'title'.width >= UIView:0x7b6c3230.width>","<NSLayoutConstraint:0x7ccdfe40 _UIAlertControllerView:0x7b6c2e50'title'.width == UIView:0x7b6efbe0.width>","<NSAutoresizingMaskLayoutConstraint:0x7c33b9d0 h=--& v=--& H:[UIView:0x7c1094e0(0)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7c00ab40 H:[UIView:0x7c0764c0(304)]>

谢谢你们.