此控制台警告对我的约束意味着什么？

Question

我有一个表格视图，并在单元格内设置了约束...我遇到了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.

这是我的viewController和约束的样子：

Answer 1

它基本上告诉您约束是冲突的，它必须自动删除其中的1个。

假设您的视图高度为40。然后，在其中放置一个视图，并告诉它从顶部开始为10，高度为20，从底部开始为0。这将导致它告诉您1个约束是错误的，必须删除才能起作用。因为您订购的高度为30，而实际高度为40。

另一件事是，在上述情况下，您实际上到底有10个倒数。这也会造成冲突，因为视图已经知道它是最底端的10，这意味着您基本上告诉编译器它的最底端是10的两次。