ios swift index 0 beyond bounds for empty array when calculate height in collectionview

Question

i want calculate height of collection view cell on HTML string. HTML string converted to string by bottom extension. but when runtime this error and crash:

*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndexedSubscript:]: index 0 beyond bounds for empty array'

my code:

extension String {
    var htmlToAttributedString: NSAttributedString? {
        guard let data = data(using: .utf8) else { return NSAttributedString() }
        do {
            return try NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding:String.Encoding.utf8.rawValue], documentAttributes: nil)
        } catch {
            return NSAttributedString()
        }
    }
    var htmlToString: String {
        return htmlToAttributedString?.string ?? ""
    }
}

in method cellForItemAt:

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    //let cell  = ....
    cell?.biographyTextView.text = artistModel?.biography?.htmlToString
}

and in method sizeForItemAt

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let htmlToString = artistModel?.biography?.htmlToString
    let size = CGSize(width: collectionView.frame.width, height: .greatestFiniteMagnitude)
    let attributes = [NSAttributedStringKey.font: UIFont.systemFont(ofSize: 15)]
    let estimatedFrame = NSString(string: htmlToString!).boundingRect(with: size, options: [.usesFontLeading, .usesLineFragmentOrigin], attributes: attributes, context: nil)
    return CGSize(width: collectionView.frame.width, height: estimatedFrame.height)
}

biography text is for example:

<p>blahblah><br /><br/><li>asd</li>....

@rmaddy when i use `NSString(string: artistModel?.biography!)` it fixed. but with htmlToString extension has error. — Farzad, Sep 05 '18 at 22:21
@rmaddy idk. perhaps this line `let htmlToString = artistModel?.biography?.htmlToString` in `sizeForItemAt` method — Farzad, Sep 05 '18 at 22:24
You need to know without guessing. Use the debugger. Where does it crash? — rmaddy, Sep 05 '18 at 22:30
@rmaddy this line `let estimatedFrame = NSString(string: htmlToString!).boundingRect(with: size, options: [.usesFontLeading, .usesLineFragmentOrigin], attributes: attributes, context: nil)` with this error: `*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndexedSubscript:]: index 0 beyond bounds for empty array'` — Farzad, Sep 05 '18 at 22:36
Your catch block should not return a new object it should return nil — Leo Dabus, Sep 05 '18 at 22:45
Btw whats the purpose of using a do try catch error handling syntax in your extension if you are ignoring the error — Leo Dabus, Sep 05 '18 at 22:47
You need to break your code down to be able to spot which array is empty — Leo Dabus, Sep 05 '18 at 22:49
@LeoDabus how to use my code with main thread? (biography text is too long string) — Farzad, Sep 05 '18 at 22:57

score 1 · Answer 1 · edited Sep 05 '18 at 22:31

1

Clean this up. Change:

let htmlToString = artistModel?.biography?.htmlToString

to:

guard let artist = artistModel, let biblio = artist.biography else {return a default size}

let htmlToString = biblio.htmlToString

edited Sep 05 '18 at 22:31

rmaddy

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answered Sep 05 '18 at 22:24

shayegh

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`artistModel` and `biography` prepared and exists. not nulled – Farzad Sep 05 '18 at 22:27

score 0 · Accepted Answer · answered Sep 05 '18 at 23:11

0

Fixed. according answer by @Leo Dabus: https://stackoverflow.com/a/28132610/2303865

problem fixed on Main Thread. before using extenstion convert html to string in sizeForItemAt. it must convert on main thread. thanks all

answered Sep 05 '18 at 23:11

Farzad

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ios swift index 0 beyond bounds for empty array when calculate height in collectionview

2 Answers2