在我的案例中，我通过设置Xcode抱怨的约束的优先级为750来设法摆脱警告，但在删除并重新插入到表后，单元格仍然使用错误的高度。

问题来自于对beginUpdates()和endpdates()的调用(在我做删除和插入的地方之间)方法被封装在UIView.animate(withDuration:)动画块中，我想在更新表时控制动画的持续时间。 删除对动画块的调用为我解决了这个问题。

格瓦拉的回答让我走上了正确的道路。我已经在我的UITableViewCell中创建了一个高度约束的出口，并且我在运行时基于一些条件改变了这个高度约束。

而不是这个——

myHeightConstraint.constant = 0.0

我写道——

myHeightConstraint.constant = CGFloat.zero

这为我解决了这个警告。基本上，hightforrowat方法中返回的任何高度都应该与运行时使用约束计算的高度相同。

99.9%的情况下，当使用自定义单元格或标头时，UITableViews的所有冲突都发生在表第一次加载时。一旦加载，你通常不会再看到冲突。

This happens because most developers typically use a fixed height or anchor constraint of some sort to layout an element in the cell/header. The conflict occurs because when the UITableView first loads/being laid out, it sets the height of its cells to 0. This obviously conflicts with your own constraints. To solve this, simply set any fixed height constraints to a lower priority (.defaultHigh). Read carefully the console message and see which constraint the layout system decided to break. Usually this is the one that needs its priority changed. You can change the priority like this:

let companyNameTopConstraint = companyNameLabel.topAnchor.constraint(equalTo: companyImageView.bottomAnchor, constant: 15)
    companyNameTopConstraint.priority = .defaultHigh

NSLayoutConstraint.activate([
            companyNameTopConstraint,
           the rest of your constraints here
            ])

No one answered it how to solve the case in storyboard. You have the case of mine, top bottom constraint with fixed height with priority 1000. That is why, when first time loading , as the table view cell height is 0, tries to set the element with the fixed height, causing a constraint conflict. (I am trying to insert 40 pixel in a 0 pixel height area, so compiler tries discarding the 40 pixel height). Once the tableview loaded, it will not generate (Like pop back to the tableview or switching tab bar tab)

所以将优先级从必需的@1000更改为高@750或低@250。第一次加载时，不考虑低优先级，然后在layoutSubviews()中调整所有约束的大小

当使用UITableViewAutomaticDimension并在单元格内的视图上更改高度约束时，我有这个错误。

我最终发现这是由于约束常数值没有四舍五入到最近的整数。

let neededHeight = width / ratio // This is a CGFloat like 133.2353
constraintPictureHeight.constant = neededHeight // Causes constraint error
constraintPictureHeight.constant = ceil(neededHeight) // All good!

与其通知表视图更新它的约束，不如尝试重新加载单元格:

[tableView beginUpdates];

[_briefCell collapse:!_showFullBriefText];

[tableView reloadRowsAtIndexPaths:@[[tableView indexPathForCell:_briefCell]] withRowAnimation:UITableViewRowAnimationNone];

[tableView endUpdates];

uiview - encapsulation - layout - height可能是表格视图在初始加载期间为单元格计算的高度，基于单元格当时的约束。