[报错]Unable to simultaneously satisfy constraints

项目中自定义Cell，控件使用autoLayout来设置约束，发现运行页面表现正常，但是控制台报如下错误：

 Unable to simultaneously satisfy constraints.

     Probably at least one of the constraints in the following list is one you don't want.

     Try this:

         () look at each constraint and try to figure out which you don't expect;

         () find the code that added the unwanted constraint or constraints and fix it.

 (

     <NSLayoutConstraint:0x10c30ee10 V:[UILabel:0x10c30ebb0'Label'(21.6667)]>,

     <NSLayoutConstraint:0x10c30f9c0 V:[UIView:0x10c30ea20()]>,

     <NSLayoutConstraint:0x10c30fab0 V:|-()-[UILabel:0x10c30ebb0'Label']   (Names: '|':UIView:0x10c30ea20 )>,

     <NSLayoutConstraint:0x10c30fb00 V:[UILabel:0x10c30ebb0'Label']-()-[UILabel:0x10c30f080'Label']>,

     <NSLayoutConstraint:0x10c30fb50 UILabel:0x10c30f080'Label'.height == UILabel:0x10c30ebb0'Label'.height>,

     <NSLayoutConstraint:0x10c30fc90 V:[UILabel:0x10c30f3d0'Label']-()-|   (Names: '|':UIView:0x10c30ea20 )>,

     <NSLayoutConstraint:0x10c30fd80 V:[UILabel:0x10c30f080'Label']-()-[UILabel:0x10c30f3d0'Label']>

 )

 Will attempt to recover by breaking constraint

 <NSLayoutConstraint:0x10c30ee10 V:[UILabel:0x10c30ebb0'Label'(21.6667)]>

 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.

问题：

表示约束发生冲突，查看错误信息，其中一个label报约束冲突：

发现在cell中设置的label高度为21.6

但实际代码中计算的label高度为21.667，并设置label高度约束为21.667

说明label约束冲突了

解决办法：

在cell中找到这个label，找到这个label的高度约束，对其优先级进行减一操作，

以前是1000，改为999，即当xib中设置的高度约束与代码中更新的高度约束不一致时，

取代码中设置的值。