iOS以编程方式删除约束问题

我有一个用于TableViewCell的xib，在这个单元格中，我有4个标签堆叠在彼此的顶部。想象一下：

Label1
Label2
Label3
Label4

我在每个标签的底部添加了一个约束，使它们之间有3个垂直空间。现在，在xib文件中执行此操作时，它还会在3的每个其他标签的顶部“创建”一个约束。所以基本上是这样的：

Label1我创建了一个底部约束，所以它也在Label2上创建了一个顶部约束，但它们指向同一个“对象”。等等，等等

问题是，在运行时，根据数据的不同，我不想显示其中一些标签。例如，我可能只需要3个标签，因此在这种情况下，我希望显示Label1、Label2和Label3。但我也不希望Label4占据任何空间，因为我不希望我的手机比它必须的大

所以我做了这样的事情：

我将label3的底部约束连接到我的视图控制器中，并将其称为label3BottomConstraint，然后执行（以及更多操作，但这是最重要的部分）：

我这样做了，但我在日志中看到这样的消息：

  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:0x7f913c1d0fc0 V:[UILabel:0x7f913e84d850'30%']-(3)-[UILabel:0x7f913e84e240'90% < 18']>"

在屏幕/模拟器上，它看起来与我想要的完全一样，但我在日志中看到了许多这样的消息：

        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:0x7feddb8b3540 V:[UIImageView:0x7feddb8b3420(0)]>",
"<NSLayoutConstraint:0x7fedd974a7a0 V:[UIImageView:0x7fedd974fd90(42)]>",
"<NSLayoutConstraint:0x7feddb9b2210 V:[UILabel:0x7feddb938360'mP'(17)]>",
"<NSLayoutConstraint:0x7feddb941250 V:[UILabel:0x7feddb9e81f0'mLabel1'(15)]>",
"<NSLayoutConstraint:0x7feddb954e50 V:[UILabel:0x7feddb94a180'fLabel1'(15)]>",
"<NSLayoutConstraint:0x7feddb91fff0 V:[UILabel:0x7feddb943cb0'fP'(17)]>",
"<NSLayoutConstraint:0x7feddb94cb10 V:|-(0)-[UIImageView:0x7feddb8b3420]   (Names: '|':UIView:0x7fedd9696640 )>",
"<NSLayoutConstraint:0x7feddb949900 V:[UIImageView:0x7feddb8b3420]-(2)-[UILabel:0x7feddb938360'mP']>",
"<NSLayoutConstraint:0x7feddb949b20 V:[UILabel:0x7feddb938360'mP']-(2)-[UILabel:0x7feddb9e81f0'mLabel1']>",
"<NSLayoutConstraint:0x7feddb949b70 V:[UILabel:0x7feddb9e81f0'mLabel1']-(3)-|   (Names: '|':UIView:0x7fedd9696640 )>",
"<NSLayoutConstraint:0x7feddb949c80 V:|-(0)-[UIImageView:0x7fedd974fd90]   (Names: '|':UIView:0x7fedd9696640 )>",
"<NSLayoutConstraint:0x7feddb949ea0 V:[UIImageView:0x7fedd974fd90]-(2)-[UILabel:0x7feddb943cb0'fP']>",
"<NSLayoutConstraint:0x7feddb949f60 V:[UILabel:0x7feddb94a180'fLabel1']-(3)-|   (Names: '|':UIView:0x7fedd9696640 )>",
"<NSLayoutConstraint:0x7feddb949fb0 V:[UILabel:0x7feddb943cb0'fP']-(2)-[UILabel:0x7feddb94a180'fLabel1']>"
     )

     Will attempt to recover by breaking constraint 
    NSLayoutConstraint:0x7fedd974a7a0 V:[UIImageView:0x7fedd974fd90(42)]

无法同时满足约束。
可能下面列表中至少有一个约束是您不想要的。试着这样做：（1）看看每个约束，试着找出你不期望的约束；（2） 找到添加了不需要的约束的代码，然后修复它。（注意：如果您看到不理解的NSAutoresizingMaskLayoutConstraints，请参阅UIView属性TranslatesAutoResizingMaskToConstraints的文档）
(
"",
"",
"",
"",
"",
"",
"",
"",
"",
"",
"",
"",
"",
""
)
将尝试通过打破约束进行恢复
NSLayoutConstraint:0x7fedd974a7a0 V:[UIImageView:0x7fedd974fd90（42）]

---

在这种情况下，我所做的任何事情似乎都没有受到重视。

您能提供更多关于您设置的约束的详细信息吗？从您描述的方式来看，因为您正在执行

label1.bottom-label2.top

间距约束，所以

label3BottomConstraint

应该引用

label4.top

。所以从你所描述的，所有应该发生的事情，就是你正在移除3磅的垂直空间，但是标签仍然挂着around@Killian我添加了一个显示更多细节的编辑。

    cell.dataContainerBottomSpaceConstraint.constant = 0;
    cell.dataContainerTopSpaceConstraint.constant = 8;
    cell.dataContainer.hidden = YES;

    cell.mImageHeightConstraint.constant = 0;
    cell.fImageHeightConstraint.constant = 0;
    cell.mImageBottomConstraint.constant = 0;
    cell.fImageBottomConstraint.constant = 0;
    cell.mImage.hidden = YES;
    cell.flmage.hidden = YES;

    cell.mPBottomConstraint.constant = 0;
    cell.fPBottomConstraint.constant = 0;
    cell.mPHeightConstraint.constant = 0;
    cell.fPLabelHeightConstraint.constant = 0;
    cell.mPLabel.hidden = YES;
    cell.fPLabel.hidden = YES;

    cell.mLine1BottomConstraint.constant = 0;
    cell.fLine1BottomConstraint.constant = 0;
    cell.mLine1HeightConstraint.constant = 0;
    cell.fLine1HeightConstraint.constant = 0;
    cell.mLine1.hidden = YES;
    cell.fLine1.hidden = YES;

        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:0x7feddb8b3540 V:[UIImageView:0x7feddb8b3420(0)]>",
"<NSLayoutConstraint:0x7fedd974a7a0 V:[UIImageView:0x7fedd974fd90(42)]>",
"<NSLayoutConstraint:0x7feddb9b2210 V:[UILabel:0x7feddb938360'mP'(17)]>",
"<NSLayoutConstraint:0x7feddb941250 V:[UILabel:0x7feddb9e81f0'mLabel1'(15)]>",
"<NSLayoutConstraint:0x7feddb954e50 V:[UILabel:0x7feddb94a180'fLabel1'(15)]>",
"<NSLayoutConstraint:0x7feddb91fff0 V:[UILabel:0x7feddb943cb0'fP'(17)]>",
"<NSLayoutConstraint:0x7feddb94cb10 V:|-(0)-[UIImageView:0x7feddb8b3420]   (Names: '|':UIView:0x7fedd9696640 )>",
"<NSLayoutConstraint:0x7feddb949900 V:[UIImageView:0x7feddb8b3420]-(2)-[UILabel:0x7feddb938360'mP']>",
"<NSLayoutConstraint:0x7feddb949b20 V:[UILabel:0x7feddb938360'mP']-(2)-[UILabel:0x7feddb9e81f0'mLabel1']>",
"<NSLayoutConstraint:0x7feddb949b70 V:[UILabel:0x7feddb9e81f0'mLabel1']-(3)-|   (Names: '|':UIView:0x7fedd9696640 )>",
"<NSLayoutConstraint:0x7feddb949c80 V:|-(0)-[UIImageView:0x7fedd974fd90]   (Names: '|':UIView:0x7fedd9696640 )>",
"<NSLayoutConstraint:0x7feddb949ea0 V:[UIImageView:0x7fedd974fd90]-(2)-[UILabel:0x7feddb943cb0'fP']>",
"<NSLayoutConstraint:0x7feddb949f60 V:[UILabel:0x7feddb94a180'fLabel1']-(3)-|   (Names: '|':UIView:0x7fedd9696640 )>",
"<NSLayoutConstraint:0x7feddb949fb0 V:[UILabel:0x7feddb943cb0'fP']-(2)-[UILabel:0x7feddb94a180'fLabel1']>"
     )

     Will attempt to recover by breaking constraint 
    NSLayoutConstraint:0x7fedd974a7a0 V:[UIImageView:0x7fedd974fd90(42)]