ios - 这个控制台警告对我的约束意味着什么？

Question

我有一个 TableView ，并在单元格内设置约束...我收到一个我不理解的约束错误。这是控制台打印:

2019-07-08 01:10:56.377538-0400 TableCellDynamicHeight[5827:393085] [LayoutConstraints] 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. 
(
    "<_UILayoutSupportConstraint:0x2835000a0 _UILayoutGuide:0x135e164f0.height == 20   (active)>",
    "<_UILayoutSupportConstraint:0x283500000 V:|-(0)-[_UILayoutGuide:0x135e164f0]   (active, names: '|':UIView:0x135e16310 )>",
    "<NSLayoutConstraint:0x283517e80 V:[_UILayoutGuide:0x135e164f0]-(0)-[UITableView:0x13682e800]   (active)>",
    "<NSLayoutConstraint:0x2835001e0 V:|-(0)-[UITableView:0x13682e800]   (active, names: '|':UIView:0x135e16310 )>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x283517e80 V:[_UILayoutGuide:0x135e164f0]-(0)-[UITableView:0x13682e800]   (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful.

这就是我的 viewController 和约束​​的样子:

Answer 1

它基本上告诉您您的约束有冲突，它必须自动删除其中的一个。

假设您有一个高度为 40 的 View 。然后你在里面放一个 View ，并告诉它距离顶部 10，高度 20，距离底部 0。这将导致它告诉您 1 个约束是错误的，必须删除才能工作。因为您命令它的高度为 30，而实际高度为 40。

另一件事是，如果在上述情况下您实际上有 10 个底部。这也会造成冲突，因为 View 已经知道它是 10 到底部，这意味着你基本上告诉编译器它的 10 到底部两次