Martin Koles Martin Koles - 5 months ago 129
iOS Question

Variable height CollectionView inside a self-sized TableView cell with AutoLayout on iOS8+

I have a

UITableView
with self-sized cell's height using
UITableViewAutomaticDimension
and AutoLayout constraints. On one of prototype cells I need to add
UICollectionView
with
UICollectionViewFlowLayout
which will layout cells vertically in a single column for Compact Size Classes or in grid of 3 columns for Regular Size Classes. The height of the collection view is therefore dynamic and the layout may change even on rotation on iPhone 6 Plus (Compact->Regular).

I setup my tableview with custom prototype cells in storyboard and add the custom collectionview into a prototype cell, AutoLayout constraints always to zero to the corresponding edge of the superview (leading, trailing, top, bottom = 0 to superview) ... collectionView->tableviewContentView->tableviewCell.

I need the variable height of the collection view to drive the height of the tableview prototype cell. So far I am always getting the following AutoLayout error on runtime.

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.


Can you please suggest the right approach to this? Thank you!

Main TableViewController:

class TableViewController: UITableViewController {
override func viewDidLoad() {
super.viewDidLoad()
tableView.estimatedRowHeight = 200.0
tableView.rowHeight = UITableViewAutomaticDimension
}
/// ... plus tableview datasource functions
}


CollectionView:

class AttachmentCollectionView: UICollectionView, UICollectionViewDataSource, UICollectionViewDelegate {

override func awakeFromNib() {
let nib = UINib(nibName: Constants.AttachmentCollectionView.cellNibName, bundle: nil)
registerNib(nib, forCellWithReuseIdentifier: Constants.AttachmentCollectionView.cellIdentifier)
collectionViewLayout = attachmentFlowLayout()
dataSource = self
delegate = self
backgroundColor = UIColor.whiteColor()
}

private func attachmentFlowLayout() -> UICollectionViewFlowLayout {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .Vertical
layout.itemSize = CGSize(width: 70, height: 50)
layout.sectionInset = UIEdgeInsets(top: 0.0, left: 0.0, bottom: 0.0, right: 0.0)
layout.minimumLineSpacing = 0.0
layout.minimumInteritemSpacing = 0.0
layout.headerReferenceSize = CGSizeMake(0.0, 0.0)
layout.footerReferenceSize = CGSizeMake(0.0, 0.0)
return layout
}
// ...plus collectionview datasource functions
}

Answer

I think implementing the tableView's delegate method tableView(_ tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat may work.

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