无法同时满足动态单元格的高度限制

Question

我有表格单元格，根据标签文字大小动态调整其高度。我还通过使它们的高度为0来使一些细胞不可见。

在viewDidLoad中：

tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 70

然后：

  func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
       let item = datasource[indexPath.row]
       if item.isVisible == true {
          return UITableViewAutomaticDimension
       }
       else{
          return 0
       }
   } 

在uitableviewcell的内容视图中，我在其下方有标签和文本字段。像这样：

=====================

TopHeightToSuperview

的UILabel

BottomSpaceToTextField

的UITextField

BottomSpaceToSuperview

=====================

细胞正确调整大小。但是我收到了这个错误：

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fd05ded2150 V:[TitleLabel(17)]   (Names: TitleLabel:0x7fd05ded0760 )>

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.
2016-06-29 17:24:03.391 invest.comQA[98164:6141441] 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:0x7fd05deed120 V:|-(15)-[TitleLabel]   (Names: TitleLabel:0x7fd05ded0760, '|':UITableViewCellContentView:0x7fd05dee8000 )>",
    "<NSLayoutConstraint:0x7fd05deed260 V:[Text Field]-(14)-|   (Names: Text Field:0x7fd05deea9a0, '|':UITableViewCellContentView:0x7fd05dee8000 )>",
    "<NSLayoutConstraint:0x7fd05deed420 V:[TitleLabel]-(15)-[Text Field]   (Names: Text Field:0x7fd05deea9a0, TitleLabel:0x7fd05ded0760 )>",
    "<NSLayoutConstraint:0x7fd05def1f00 'UIView-Encapsulated-Layout-Height' V:[UITableViewCellContentView:0x7fd05dee8000(0)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fd05deed420 V:[TitleLabel]-(15)-[Text Field]   (Names: Text Field:0x7fd05deea9a0, TitleLabel:0x7fd05ded0760 )>

为什么？