Layouting dynamic subviews in a UITableviewCell, make constrains to margins - ios

Question

In my app, I have a UITableViewCell which can contain an arbitrary UIView (or subclass hereof). I want the view to fit into the UITableViewCell's contentView's margins. And the cell height will be adjusted to the needs of my view.
I've tried various things but with no positive result.
Here's the code. It does not work. :(
It does not fit the margins and the content is wider than the screen size.
What to do?
class CustomView: UIStackView {
class func viewFromNib() -> CustomView {
guard let view = NSBundle(forClass: CustomView.self).loadNibNamed("CustomView", owner: nil, options: nil).first as? CustomView else {fatalError("CustomView not found")}
return view
}
}
class ViewController: UITableViewController {
let customView = CustomView.viewFromNib()
var containerCell: ContainerTableViewCell?
override func viewDidLoad() {
super.viewDidLoad()
containerCell = ContainerTableViewCell.cell(customView, height: nil)
tableView.reloadData()
tableView.estimatedRowHeight = 40
tableView.rowHeight = UITableViewAutomaticDimension
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
return containerCell ?? UITableViewCell()
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 1
}
}
class ContainerTableViewCell: UITableViewCell {
var singleView: UIView?
class func cell(view: UIView, height: CGFloat?) -> ContainerTableViewCell {
let cell = ContainerTableViewCell()
cell.setup(view, height: height)
return cell
}
func setup(view: UIView, height: CGFloat?) {
singleView = view
contentView.addSubview(singleView!)
let margins = contentView.layoutMarginsGuide
singleView?.topAnchor.constraintEqualToAnchor(margins.topAnchor).active = true
singleView?.leadingAnchor.constraintEqualToAnchor(margins.leadingAnchor).active = true
singleView?.trailingAnchor.constraintEqualToAnchor(margins.trailingAnchor).active = true
singleView?.bottomAnchor.constraintEqualToAnchor(margins.bottomAnchor).active = true
setNeedsLayout()
if let height = height {
contentView.heightAnchor.constraintEqualToConstant(height).active = true
}
}
}

Answer 1

You should implement
optional func tableView(_ tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat
in your viewController and to know the height of each cell when refreshing the table.

Answer 2

cellForRowAtIndexPath must use a dequeue family method to get your table cell instance:
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UITableView_Class/#//apple_ref/occ/instm/UITableView/dequeueReusableCellWithIdentifier:forIndexPath:
Such that the object will be created through its regular constructor, not your factory method. You don't have that flexibility.
So in your subclass, put your generic constraints in awakeFromNib or an overridden constructor. Don't forget to account for the auto-resizing mask which interferes with programmatic constraints, so this field must be set to false:
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIView_Class/#//apple_ref/occ/instp/UIView/translatesAutoresizingMaskIntoConstraints
Finally, within the cellForRowAtIndexPath, you can modify the constraints of the UITableViewCell instance returned by the dequeue call, to get your custom height in there.
Good luck!