动态调整集合视图单元格的大小

Question

I have this older code example that I updated but I am still a newbie and can't figure out how to fix this one error:

In the class that holds the collection view:

var array = ["Just testing this out"]

Now in the UICollectionViewDelegateFlowLayout extension:

private func estimateFrameForText(text: String) -> CGRect {
    //we make the height arbitrarily large so we don't undershoot height in calculation
    let height: CGFloat = 1000

    let size = CGSize(width: 398, height: height)
    let options = NSStringDrawingOptions.usesFontLeading.union(.usesLineFragmentOrigin)
    let attributes = [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 17, weight: UIFont.Weight.light)]

    return NSString(string: text).boundingRect(with: size, options: options, attributes: attributes, context: nil)
}

Also:

private func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    var height: CGFloat = 295
    //we are just measuring height so we add a padding constant to give the label some room to breathe!
     var padding: CGFloat = 14
    //estimate each cell's height
    if let text = array[indexPath.item].text {
          height = estimateFrameForText(text).height + padding
     }
     return CGSize(width: 398, height: height)    }

This is where I get the error:

if let text = array[indexPath.item].text

And here's the UILabel from the collection view cell class I have no idea where to implement:

@IBOutlet weak var TextPosted: UILabel!

Answer 1

Your test array needs some adjusting. Try declaring it as an optional (since it likely will be with actual data loaded from somewhere).

var array: [String]? = ["Just testing this out", "Another test"]

Then this:

override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return array?.count ?? 0
}

Then update your if let statement in your collecitonView sizeForItemAtIndexPath function:

if let text = array?[indexPath.item]{
}

On a side note, I wrote an open-source extension to measure string size for things like this a few days ago.

Hope this helps.