如何在运行时更改约束优先级 - How can I change constraints priority in run time

问题：

I have a view which has dynamic height and I am trying to change this view height priority in run time.我有一个具有动态高度的视图，我正在尝试在运行时更改此视图高度优先级。

Here is my part of code;这是我的代码部分；

if (index == 0) {

    surveyViewHeightConstraint.constant = 0;
    surveyViewHeightConstraint.priority = 1000;

} else if (index == 1) {

    surveyViewHeightConstraint.constant = 163;
    surveyViewHeightConstraint.priority = 500;

}

I am changing index with a button action.我正在通过按钮操作更改索引。 When I run this code, I am getting this error:当我运行此代码时，出现此错误：

*** Assertion failure in -[NSLayoutConstraint setPriority:], /SourceCache/Foundation/Foundation-1141.1/Layout.subproj/NSLayoutConstraint.m:174

What is my mistake in here?我在这里有什么错误？

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解决方案：

参考： https://stackoom.com/en/question/26qx1