Ios 无法同时满足单个约束

我有一个奇怪的案例——我会尝试隔离，但我想在此期间我会提出一个问题。我有一个具有高度约束的UILabel。当我尝试将高度设置为0时，会出现以下错误：

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:0x7b9b5d90 V:[UILabel:0x7b9c6cf0(0)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7b9b5d90 V:[UILabel:0x7b9c6cf0(0)]>

Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

让我感到困惑的是，错误表示无法同时满足约束，但只显示一个约束。它还可以通过打破单一约束进行恢复

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约束如何与自身冲突？

如何设置此约束？我有一个指向在IB中创建的约束的IBOutlet，并且我在IBOutlet属性上设置了常量属性。对于从nib加载的UIView上的宽度约束，我也有相同的问题，约束是在代码中创建的。发帖后你发现了什么吗？我不相信我找到了答案，我必须从头开始重新设计，我知道UILabel有自己的布局，所以可能与基于文本的自动调整有关？