当一个视图被删除有约束，会发生什么 [英] What happens with constraints when a view is removed

问题描述

我的问题很简单，但我无法找到的文档中的任何信息。

The question I have is simple but I couldn't find any information in the documentation.

在一个视图从视图层次结构中删除（或移动到另一个视图）与布局约束，会发生什么？

What happens with layout constraints when a view is removed from the view hierarchy (or moved to another view)?

例如，让我们的容器 C 与子视图 A 和 B 。集装箱 C 持有一定的制约。然后我们调用 [A removeFromSuperview] 。与 A ？

For example, let's have container C with subviews A and B. Container C holds some constraints. Then we call [A removeFromSuperview]. What happens with the constraints for A?

如果我们添加 A 则正好 C 一遍吗？

What then happens if we add A to C again?

推荐答案

约束被删除。如果再次加A，你将不得不做出新的约束，或者如果保存约束你删除之前，你可以添加他们回来。当我做这样的事情，我保存这样的约束视图称为视图1：

The constraints are removed. If you add A again, you will have to make new constraints for it, or if you save the constraints before you remove A, you can add them back. When I do something like this, I save the constraints like this for a view called view1:

self.portraitConstraints = [NSMutableArray new];
for (NSLayoutConstraint *con in self.view.constraints) {
    if (con.firstItem == self.view1 || con.secondItem == self.view1) {
       [self.portraitConstraints addObject:con];
    }
}

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