Programatic constraints collapsing cell view

Question

I am developing a UITableViewCell that starts as a xib, has views added to it programmatically, and has a dynamically sized height. However, it looks like when adding the programatic views with constraints, it is conflicting with the auto-resize constraint initially applied to the xib, and causing issues. Please see below:

Dequeuing my cells:

//Table Delegate/Datasource
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    var cell:S360SSessionMatchTableCell? = tableView.dequeueReusableCellWithIdentifier(XIBFiles.SESSIONMATCHTABLECELL + String(indexPath.row)) as? S360SSessionMatchTableCell

    if ((cell == nil)){
        tableView.registerNib(UINib(nibName: XIBFiles.SESSIONMATCHTABLECELL, bundle: nil), forCellReuseIdentifier: XIBFiles.SESSIONMATCHTABLECELL + String(indexPath.row))
        cell = tableView.dequeueReusableCellWithIdentifier(XIBFiles.SESSIONMATCHTABLECELL + String(indexPath.row)) as? S360SSessionMatchTableCell
    }

    cell!.setupEvents(sessionMatches[indexPath.row]["sessions"]! as! [[String:String]])

    return cell!
}

Setup Events Method in Custom UITableViewCell:

func setupEvents(events:[[String:String]]){

    //Set up start and end times
    self.startTimeLbl.text = events[0]["startTime"]!
    self.endTimeLbl.text = events[events.count - 1]["endTime"]!

    //Set up events
    var pastEventView:S360SScheduledEventView? = nil
    var pastEvent:[String:String]? = nil
    for (index, event) in events.enumerate(){
        var topAnchor:NSLayoutConstraint!

        //Create event view
        let eventView:S360SScheduledEventView = NSBundle.mainBundle().loadNibNamed(XIBFiles.SCHEDULEDEVENTVIEW, owner: self, options: nil)[0] as! S360SScheduledEventView

        //Deal with first view added
        if pastEvent == nil{

            //Top anchor setup for first view
            topAnchor = NSLayoutConstraint(item: eventView, attribute: .Top, relatedBy: .Equal, toItem: toLbl, attribute: .Bottom, multiplier: 1, constant: 10)
        }
        else{

            //Check for a break
            let timeFormatter:NSDateFormatter = NSDateFormatter()
            timeFormatter.dateFormat = "hh:mm a"
            let startTime = timeFormatter.dateFromString(pastEvent!["endTime"]!)
            let endTime = timeFormatter.dateFromString(event["startTime"]!)
            if startTime != endTime {

                //Create break view
                let breakView = NSBundle.mainBundle().loadNibNamed(XIBFiles.SCHEDULEDBREAKVIEW, owner: self, options: nil)[0] as! S360SScheduledBreakView

                //Setup breakview constraints
                let bTopAnchor = NSLayoutConstraint(item: breakView, attribute: .Top, relatedBy: .Equal, toItem: pastEventView, attribute: .Bottom, multiplier: 1, constant: 0)
                let bLeftAnchor = NSLayoutConstraint(item: breakView, attribute: .Leading, relatedBy: .Equal, toItem: self.contentView, attribute: .LeadingMargin, multiplier: 1, constant: 0)
                let bRightAnchor = NSLayoutConstraint(item: breakView, attribute: .Trailing, relatedBy: .Equal, toItem: self.contentView, attribute: .TrailingMargin, multiplier: 1, constant: 0)
                let bHeightAnchor = NSLayoutConstraint(item: breakView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 30)

                //Add break view and constraints
                self.addSubview(breakView)
                self.addConstraints([bTopAnchor, bLeftAnchor, bRightAnchor, bHeightAnchor])

                //Top anchor setup for subsequent view
                topAnchor = NSLayoutConstraint(item: eventView, attribute: .Top, relatedBy: .Equal, toItem: breakView, attribute: .Bottom, multiplier: 1, constant: 0)
            }
            else{

                //Top anchor setup for subsequent views
                topAnchor = NSLayoutConstraint(item: eventView, attribute: .Top, relatedBy: .Equal, toItem: pastEventView, attribute: .Bottom, multiplier: 1, constant: 0)
            }

        }

        //Setup other anchors
        let leftAnchor = NSLayoutConstraint(item: eventView, attribute: .Leading, relatedBy: .Equal, toItem: self.contentView, attribute: .LeadingMargin, multiplier: 1, constant: 0)
        let rightAnchor = NSLayoutConstraint(item: eventView, attribute: .Trailing, relatedBy: .Equal, toItem: self.contentView, attribute: .TrailingMargin, multiplier: 1, constant: 0)
        let heightAnchor = NSLayoutConstraint(item: eventView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 60)

        //Setup event view
        eventView.iconImg.image = Images.get_event_image(event["title"]!)
        eventView.titleLbl.text = event["title"]!
        eventView.courtLbl.text = "court" + event["court"]!
        eventView.timeLbl.text = event["startTime"]! + " to " + event["endTime"]!

        //Add event view and constraints
        self.addSubview(eventView)
        self.addConstraints([topAnchor, leftAnchor, rightAnchor, heightAnchor])

        //Prepare for next iteration
        pastEventView = eventView
        pastEvent = event

        //Set up last cell with bottom bound
        if index == events.count - 1 {
            let bottomAnchor = NSLayoutConstraint(item: eventView, attribute: .Bottom, relatedBy: .Equal, toItem: self.contentView, attribute: .BottomMargin, multiplier: 1, constant: 0)
            self.addConstraint(bottomAnchor)
        }

    }
}

Constraints in xib:

This is the error I get (pasted once, but it occurs for each cell):

   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.
2016-07-05 15:13:01.654 Shoot360 Scheduler[32779:642808] 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) 
(
    "<NSAutoresizingMaskLayoutConstraint:0x7fedd85d5590 h=--& v=--& V:[UITableViewCellContentView:0x7fedda431120(44)]>",
    "<NSLayoutConstraint:0x7fedda43a7e0 V:[Shoot360_Scheduler.S360SScheduledEventView:0x7fedda438b20(60)]>",
    "<NSLayoutConstraint:0x7fedda436590 UITableViewCellContentView:0x7fedda431120.topMargin == UILabel:0x7fedda4312a0'10:00 AM'.top - 15>",
    "<NSLayoutConstraint:0x7fedda436630 UILabel:0x7fedda431c00'to'.top == UILabel:0x7fedda4312a0'10:00 AM'.top>",
    "<NSLayoutConstraint:0x7fedda433b60 V:[UILabel:0x7fedda431c00'to']-(10)-[Shoot360_Scheduler.S360SScheduledEventView:0x7fedda438b20]>",
    "<NSLayoutConstraint:0x7fedda445910 V:[Shoot360_Scheduler.S360SScheduledEventView:0x7fedda4443f0(60)]>",
    "<NSLayoutConstraint:0x7fedda448310 V:[Shoot360_Scheduler.S360SScheduledEventView:0x7fedda438b20]-(0)-[Shoot360_Scheduler.S360SScheduledEventView:0x7fedda4443f0]>",
    "<NSLayoutConstraint:0x7fedda449a00 V:[Shoot360_Scheduler.S360SScheduledEventView:0x7fedda448540(60)]>",
    "<NSLayoutConstraint:0x7fedda4479e0 V:[Shoot360_Scheduler.S360SScheduledEventView:0x7fedda4443f0]-(0)-[Shoot360_Scheduler.S360SScheduledEventView:0x7fedda448540]>",
    "<NSLayoutConstraint:0x7fedda44a100 Shoot360_Scheduler.S360SScheduledEventView:0x7fedda448540.bottom == UITableViewCellContentView:0x7fedda431120.bottomMargin>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fedda436590 UITableViewCellContentView:0x7fedda431120.topMargin == UILabel:0x7fedda4312a0'10:00 AM'.top - 15>

Row height is being set to dynamic:

override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        //Styling
        showAllBtn.layer.cornerRadius = Numbers.CORNERRADIUS

        sessionsTbl.rowHeight = UITableViewAutomaticDimension
        sessionsTbl.estimatedRowHeight = 500
        sessionsTbl.layer.borderColor = Colors.REALLIGHTGREY.CGColor
        sessionsTbl.layer.borderWidth = Numbers.BORDERREG
        sessionsTbl.layer.cornerRadius = Numbers.CORNERRADIUS
        sessionsTbl.separatorStyle = UITableViewCellSeparatorStyle.None
    }

 func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        return UITableViewAutomaticDimension
    }

Answer 1

The constraint

V:[UITableViewCellContentView:0x7fedda431120(44)

means that rowHeight in your table is set to the default value of 44pt while you want the cell height to be dynamic. You will have to set rowHeight to UITableViewAutomaticDimension and also set estimatedRowHeight.

Also note that cells are reused therefore you will have to remove all previously added views everytime you call setupEvents.

Also note you should not call tableView.registerNib(...) from inside cellForRow method. The good place to register cells is inside viewDidLoad.

Answer 2

It seems you've made life much more complicated for yourself than it needs to be.

If we look at what you currently have:

1. a table with 1 section and many rows
2. 1 cell subclass
3. each row has an arbitrary number of subviews added on the fly
4. each subview is pinned to each other with constraints
5. each cell is explicitly instantiated for each row, not properly reused
6. cells don't have their subviews removed when they are reused

this doesn't fit well with a table view and means you're writing a lot of code and trying to cram it all into one place.

Looking at your data it would be better to have something like:

1. a table with multiple sections, each section having multiple rows
2. 1 section per session
3. 1 row per 'event'
4. 1 section header class with date labels
5. 2 cell subclasses, 1 for an event and one for a break
6. no views added on the fly

In this scenario your constraints are trivial and there are no constraints being added in code, you just set a bit of data and everything else just works. This scheme also breaks down your concerns and separates out the code for each different part into logical parts.

Rather than try to fix your existing issue you should step back and look at your approach.