Swift无法在prepareForSegue中同时满足约束错误？

Question

我尝试在控制器之间传递数据

第一控制器：

class CreateStatmentFieldsController: UITableViewController, DetailsDelegate {

    @IBOutlet weak var violationLabel: UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()

        // Uncomment the following line to preserve selection between presentations
        // self.clearsSelectionOnViewWillAppear = false

        // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
        // self.navigationItem.rightBarButtonItem = self.editButtonItem()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func violationLabelDelegateMethodWithString(string: String) {
        violationLabel.text = string
    }

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
        if (segue.identifier == "violationSegue") {
            let controller = segue.destinationViewController as CreateStatmentViolationController
            controller.delegate = self
        }
    }

第二控制器：

protocol DetailsDelegate {
    func violationLabelDelegateMethodWithString(string: String)
}

class CreateStatmentViolationController: UITableViewController {

    var delegate: DetailsDelegate!

    @IBOutlet weak var backButton: UIBarButtonItem!
    let violations = ["Парковка вторым рядом", "Парковка под знаком \"остановка запрещена\"", "Парковка на тротуаре", "Парковка на пешеходном переходе", "Парковка на месте для инвалидов"]


    override func viewDidLoad() {
        super.viewDidLoad()

    }

    @IBAction func donePressed(b:UIBarButtonItem) {
        self.dismissViewControllerAnimated(true, completion: {})
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        tableView.deselectRowAtIndexPath(indexPath, animated: true)

        let row = indexPath.row
        delegate.violationLabelDelegateMethodWithString("sa")//violations[row]

        self.dismissViewControllerAnimated(true, completion: {})
    }

    // MARK: - Table view data source
//
    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        // #warning Potentially incomplete method implementation.
        // Return the number of sections.
        return 1
    }
//
    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // #warning Incomplete method implementation.
        // Return the number of rows in the section.
        return violations.count
    }


    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCellWithIdentifier("vilolationCell", forIndexPath: indexPath) as UITableViewCell
        let row = indexPath.row
        cell.textLabel?.text = violations[row]

        // Configure the cell...

        return cell
    }

但是然后我打开secont控制器我有错误：

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. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
    "<NSLayoutConstraint:0x7fdf9a455e70 H:[UIView:0x7fdf9a49ed70(400)]>",
    "<NSLayoutConstraint:0x7fdf9a490c80 H:|-(0)-[UIView:0x7fdf9a49ed70]   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",
    "<NSLayoutConstraint:0x7fdf9a490e00 UIScrollView:0x7fdf9a4958d0.centerX == UIView:0x7fdf9a49ed70.centerX>",
    "<NSLayoutConstraint:0x7fdf9a490730 H:[UIScrollView:0x7fdf9a4958d0]-(0)-|   (Names: '|':UIView:0x7fdf9a463bb0 )>",
    "<NSLayoutConstraint:0x7fdf9a491230 H:|-(0)-[UIScrollView:0x7fdf9a4958d0]   (Names: '|':UIView:0x7fdf9a463bb0 )>",
    "<NSLayoutConstraint:0x7fdf9a4ae900 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7fdf9a463bb0(375)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fdf9a455e70 H:[UIView:0x7fdf9a49ed70(400)]>

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.
2015-04-07 01:45:52.768 pin[8690:51798] 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. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
    "<NSLayoutConstraint:0x7fdf9a49ef70 H:[UIView:0x7fdf9a5a7250(390)]>",
    "<NSLayoutConstraint:0x7fdf9a495c00 H:[UIView:0x7fdf9a49ed70]-(0)-|   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",
    "<NSLayoutConstraint:0x7fdf9a490c80 H:|-(0)-[UIView:0x7fdf9a49ed70]   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",
    "<NSLayoutConstraint:0x7fdf9a490e00 UIScrollView:0x7fdf9a4958d0.centerX == UIView:0x7fdf9a49ed70.centerX>",
    "<NSLayoutConstraint:0x7fdf9a493b00 H:|-(5)-[UIView:0x7fdf9a5a7250]   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",
    "<NSLayoutConstraint:0x7fdf9a480580 H:[UIView:0x7fdf9a5a7250]-(5)-|   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",
    "<NSLayoutConstraint:0x7fdf9a490730 H:[UIScrollView:0x7fdf9a4958d0]-(0)-|   (Names: '|':UIView:0x7fdf9a463bb0 )>",
    "<NSLayoutConstraint:0x7fdf9a491230 H:|-(0)-[UIScrollView:0x7fdf9a4958d0]   (Names: '|':UIView:0x7fdf9a463bb0 )>",
    "<NSLayoutConstraint:0x7fdf9a4ae900 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7fdf9a463bb0(375)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fdf9a49ef70 H:[UIView:0x7fdf9a5a7250(390)]>

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.
2015-04-07 01:45:52.774 pin[8690:51798] Warning once only: Detected a case where constraints ambiguously suggest a height of zero for a tableview cell's content view. We're considering the collapse unintentional and using standard height instead.

如果我删除“ prepareForSegue”功能，则所有工作正常，第二个视图可以完美打开和关闭，但是我需要将数据发送到filrst控制器。

Answer 1

除非过于简化，否则错误似乎很简单。

因此，这是调试器的罪魁祸首–

"<NSLayoutConstraint:0x7fdf9a455e70 H:[UIView:0x7fdf9a49ed70(400)]>",
"<NSLayoutConstraint:0x7fdf9a490c80 H:|-(0)-[UIView:0x7fdf9a49ed70]   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",

"<NSLayoutConstraint:0x7fdf9a495c00 H:[UIView:0x7fdf9a49ed70]-(0)-|   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",
"<NSLayoutConstraint:0x7fdf9a490c80 H:|-(0)-[UIView:0x7fdf9a49ed70]   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",

在两个调试器打印输出中，都会出现UIView：0x7fdf9a49ed70。 可能要花一些时间，但似乎此视图的高度已明确设置为400。 然后将其两次约束到其超级视图的顶部，一次约束到其超级视图的底部。

在该打印输出下，对这些感到不安。

"<NSLayoutConstraint:0x7fdf9a49ef70 H:[UIView:0x7fdf9a5a7250(390)]>",
"<NSLayoutConstraint:0x7fdf9a493b00 H:|-(5)-[UIView:0x7fdf9a5a7250]   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",
"<NSLayoutConstraint:0x7fdf9a480580 H:[UIView:0x7fdf9a5a7250]-(5)-|   (Names: '|':UIScrollView:0x7fdf9a4958d0 )>",

因此，视图再次被限制在其superView的顶部和底部。 该视图的显式高度也设置为390点。

看起来，在segue期间的某个时候甚至在segue之后，superView的高度分别不等于390或400，因此无法满足约束。 如果我是你，我要么没有明确设定的若干意见的高度，只有约束顶部和底部或设置高度和约束他们的顶部或底部。 这三个约束不是必需的，在这种情况下，不可能同时实现。