i自动通过NSLayoutConstraint代码自动布局以设置视图的高度，并且我有一个奇怪的错误：当我使用fraction number（例如324.867）来设置视图的高度时。它增加了错误 Unable to simultaneously satisfy constraints。
但是，如果我将324.867圆向324。错误消失了。
任何人都可以解释为什么会发生吗？
这是我的代码：
let estimateSizeOfTopic = CGSize(width: self.frame.width - 10.0, height: 1000.0)
let attributeOfTopic = [NSFontAttributeName: UIFont.systemFont(ofSize: 14)]
let estimateHeight = NSString(string: topicTitle.text!).boundingRect(with: estimateSizeOfTopic, options: .usesLineFragmentOrigin, attributes: attributeOfTopic, context: nil).height
NSLayoutConstraint(item: topicTitle, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: estimateHeight).isActive = true
NSLayoutConstraint(item: topicTitle, attribute: .top, relatedBy: .equal, toItem: superView, attribute: .top, multiplier: 1.0, constant: 5.0).isActive = true
NSLayoutConstraint(item: topicTitle, attribute: .left, relatedBy: .equal, toItem: superView, attribute: .left, multiplier: 1.0, constant: 5.0).isActive = true
NSLayoutConstraint(item: topicTitle, attribute: .right, relatedBy: .equal, toItem: superView, attribute: .right, multiplier: 1.0, constant: -5.0).isActive = true
NSLayoutConstraint(item: topicTitle, attribute: .bottom, relatedBy: .equal, toItem: superView, attribute: .bottom, multiplier: 1.0, constant: -5.0).isActive = true
//我的监督纸没有任何限制...我是这样编码的，因为我想通过我的入围高度自动设置超级图的高度（Table View Cell自动尺寸）
错误发生在第一个约束。
//If I use this line of code. It raise an error
NSLayoutConstraint(item: topicTitle, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: estimateHeight).isActive = true
//If I use this line of code instead. The error is gone
NSLayoutConstraint(item: topicTitle, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: round(estimateHeight)).isActive = true
我将estimateHeight弄圆，因为如果我不围绕它，它会引起错误。但是激励有错误。我视图中的每个事情仍然看起来正确
这是调试窗口所说的：
[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.
(
"<NSLayoutConstraint:0x608000484560 UITextView:0x7f9049080c00'It is a long established ...'.height == 324.867 (active)>",
"<NSLayoutConstraint:0x608000285280 V:|-(5)-[UITextView:0x7f9049080c00'It is a long established ...'] (active, names: '|':SatacusWorld.PostViewCell:0x7f9049096a00'postIdentifier' )>",
"<NSLayoutConstraint:0x60800029fe50 UITextView:0x7f9049080c00'It is a long established ...'.bottom == SatacusWorld.PostViewCell:0x7f9049096a00'postIdentifier'.bottom - 5 (active)>",
"<NSLayoutConstraint:0x60800029fcc0 'UIView-Encapsulated-Layout-Height' SatacusWorld.PostViewCell:0x7f9049096a00'postIdentifier'.height == 334.8 (active)>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x608000484560 UITextView:0x7f9049080c00'It is a long established ...'.height == 324.867 (active)>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
这绝对是一个好奇的错误，因为这些错误中的数学汇总（从字面上看）。
但是，并不奇怪：在布局约束中使用boundingRect(with:options:attributes:context:)中的估计值，并期望以后与自动布局计算匹配，即使示例的精确性不如此，则可能会失败。这是由于排版的详细信息，以及可能以不同尺度呈现字体呈现的详细信息。
您可能想问，您能否避免在此文本视图上设置高度约束？由于您希望整个文本出现，因此请确保将UITextView属性scrollEnabled设置为false。这将导致其在适当的时间（设置水平界限时）为自动布局引擎提供正确的文本大小。如果在单元格中使用自动细胞尺寸，则应正确大小和单元格。希望这可以帮助。
我弄清楚为什么会发生错误。因为我使用了这两条代码
的自动尺寸表视图tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 100.0
，在后台，UITableViewAutomaticDimension将自动计算我的单元高度，然后将该数字圆成1个小数位
例如：
如果我的总细胞高度为： 324.833
将该数字围绕324.8
这样。电池的总高度（324.833）大于单元的高度（324.8）
为了解决该错误，我只是在UITableViewAutomaticDimension围绕它围绕它的数字