获取NSLayoutConstraints关联视图 [英] getting NSLayoutConstraints associated view

问题描述

我试图遍历视图约束.

我在view1中添加了:顶部，尾部，前导和高度限制.

I added to view1: top, trailing, leading and height constraints.

顶部，尾部和前导是ViewControllers主视图.

top, trailing and leading are to the main ViewControllers view.

如果我遍历view1的约束，我只会看到高度约束.

if i loop through view1's constraints i only see the height constraint.

for constraint in view1.constraints {
    print(constraint)
}

NSLayoutConstraint:0x6180000968a0 UIView:0x7fae6b409dd0.height == 146(活动)

NSLayoutConstraint:0x6180000968a0 UIView:0x7fae6b409dd0.height == 146 (active)

因此我遍历了其超级视图约束(ViewControllers主视图)，并且遇到了很多约束，其中一些约束与view1相关.

so i looped through its superviews constraints (the ViewControllers main view) and i got lots of constraints some of them are associated with view1.

for constraint in view1.superview?.constraints {
    print(constraint)
}

NSLayoutConstraint:0x618000096670 H:|-(0)-[UIView:0x7fae6b409dd0](活动，名称:'|':UIView:0x7fae6b40a180)

NSLayoutConstraint:0x618000096670 H:|-(0)-[UIView:0x7fae6b409dd0] (active, names: '|':UIView:0x7fae6b40a180 )

NSLayoutConstraint:0x6180000974d0 H:[UIView:0x7fae6b409dd0]-(0)-| (活动，名称:"|":UIView:0x7fae6b40a180)

NSLayoutConstraint:0x6180000974d0 H:[UIView:0x7fae6b409dd0]-(0)-| (active, names: '|':UIView:0x7fae6b40a180 )

NSLayoutConstraint:0x618000097520 V:|-(0)-[UIView:0x7fae6b409dd0](活动，名称:'|':UIView:0x7fae6b40a180)

NSLayoutConstraint:0x618000097520 V:|-(0)-[UIView:0x7fae6b409dd0] (active, names: '|':UIView:0x7fae6b40a180 )

还有一些我不在乎的东西.

and i get a few more that i dont care about.

所以我的问题是我想遍历view1的所有superviews约束，而只获取与之关联的约束.

So my problem is that i want to loop through all of view1's superviews constraints and get only the ones that are associated with it.

在此示例中，UIView:0x7fae6b409dd0是view1.

In this example UIView:0x7fae6b409dd0 is view1.

但是我不知道如何获得该财产.

But i cant figure out how to get that property.

谢谢

如果我打印出constraint.firstAnchor，我可以获得更多信息，但仍无法获取相关视图.

If i print out constraint.firstAnchor i get some more information but still cant get the associated view.

NSLayoutXAxisAnchor:0x608000265480"UIView:0x7fae6b409dd0.leading">

NSLayoutXAxisAnchor:0x608000265480 "UIView:0x7fae6b409dd0.leading">

NSLayoutXAxisAnchor:0x608000265480"UIView:0x7fae6b409dd0.trailing">

NSLayoutXAxisAnchor:0x608000265480 "UIView:0x7fae6b409dd0.trailing">

NSLayoutXAxisAnchor:0x608000265480"UIView:0x7fae6b409dd0.top">

NSLayoutXAxisAnchor:0x608000265480 "UIView:0x7fae6b409dd0.top">

推荐答案

您可以使用NSLayoutConstraint的firstItem和secondItem属性来获取与约束相关的视图.请注意，secondItem是可选，并且必须解包.

You can use the firstItem and secondItem properties of NSLayoutConstraint to get the views related to the constraint. Note that secondItem is an Optional and must be unwrapped.

然后，您可以使用===运算符比较它是否是同一对象:

Then you can use the === operator to compare if it is the same object:

let constraints = view1.superview!.constraints
var count = 0

print("superview has \(constraints.count) constraints")

for constraint in constraints {
    if constraint.firstItem === view1 {
        count += 1
        print(constraint)
    } else if let secondItem = constraint.secondItem, secondItem === view1 {
        count += 1
        print(constraint)
    }
}

print("\(count) of them relate to view1")

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