Question

我在运行时遇到此错误：

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7ff70350c8a0 UITableViewCellContentView:0x7ff7058511c0.trailingMargin == UIView:0x7ff705851f00.trailing>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2016-08-29 16:53:12.533 xxxx[7125:4051730] 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. 
(
    "<NSLayoutConstraint:0x7ff705a0aca0 UITableViewCellContentView:0x7ff705853420.trailingMargin == UIView:0x7ff7058546f0.trailing - 10>",
    "<NSLayoutConstraint:0x7ff705a0ad90 UITableViewCellContentView:0x7ff705853420.trailingMargin == UIView:0x7ff7058546f0.trailing>"
)

但是，我无法确定它的来源

UITableViewCellContentView：0x7ff705853420.trailingMargin == 的UIView：0x7ff7058546f0.trailing

我在IDE中找不到。我已经尝试在我设置约束的位置搜索代码 - 但就我所知，没有任何与错误匹配的内容。

是否有可能定义了Xcode IDE没有显示的约束？

Answer 1

当约束中断时，您可以扩展NSLayoutConstraint并覆盖description以返回稍微更人性化的信息：

extension NSLayoutConstraint {
    override public var description: String {
        let id = identifier ?? "NO ID"
        return "id: \(id), constant: \(constant)"
    }
}

这个繁琐的部分是你必须为每个约束手动设置一个id，尽管你可以通过注释掉扩展来限制所需的工作量，并且只设置与标准约束警告相关的约束的标识符。

Answer 2

您可以尝试打开MainStoryBoard作为源代码并在那里搜索。问题是你有两个相同的约束（UIView的尾随边距），其中一个是0，另一个是10.它可能没有从故事板的源代码中删除。

xcode在运行时报告约束错误 - 但找不到它？

2 个答案: