Swift无法在prepareForSegue中同时满足约束错误？

Question

I try pass data between controllers

First controller:

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
        }
    }

Second Controller:

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
    }

but then i open secont controller i have bug:

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.

If i remove "prepareForSegue" func, all worked, second view open and close perfectly, but i need send data to filrst controller.

Answer 1

The error seems to be pretty straight forward unless it is an oversimplification.

So these are the culprits according to the debugger –

"<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 )>",

In both debugger printouts UIView:0x7fdf9a49ed70 appears. It might take some playing around with, but it seems like this view's height is set to 400 explicitly. It is then constrained twice to the top of its superview and once to the bottom of the superview.

Under that printout it is upset about these.

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

So again a view is constrained to the top and bottom of its superView. That view also has an explicit height set to 390 points.

It looks like, at some point during the segue and maybe even after the segue, the superView's height does not equal 390 or 400 respectively and for that reason the constraints cannot be satisfied. If I were you, I would either not explicitly set the views' height and only constrain top and bottom or set the height and constrain them to either the top or the bottom. All three constraints aren't necessary and in this case aren't simultaneously possible.