UICollectionViewCell subclass cannot use backgroundView property?

Question

Created Dec ’20

Replies 2

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I made a subclass of UICollectionViewCell and Swift is complaining that I'm not allowed to use superclass properties like bounds, backgroundView or selectedBackgroundView. This very code was given by Appleʼs documentation so I don't understand why it's disallowed.

I declared class MyCollectionViewCell: UICollectionViewCell method awakeFromNib.

Code Block class MyCollectionViewCell: UICollectionViewCell {
...
override class func awakeFromNib() {
...
let redView = UIView(frame: bounds)
redView.backgroundColor =  colorLiteral(red: 1, green: 0, blue: 0, alpha: 1)
self.backgroundView = redView
let blueView = UIView(frame: bounds)
blueView.backgroundColor =  colorLiteral(red: 0, green: 0, blue: 1, alpha: 1)
self.selectedBackgroundView = blueView

Xcode 12.2 gives an error about bounds, backgroundView, and selectedBackgroundView saying stuff like "Instance member 'bounds' cannot be used on type 'MyCollectionViewCell'".

If I declare a variable as UICollectionViewCell I can set these properties in it, but a function in a subclass of UICollectionViewCell cannot access its own properties?

Answered by OOPer in 654408022

The problem exists in this line:

Code Block     override class func awakeFromNib() {

The method awakeFromNib() which you want to override is an instance method, not a class method.
Remove the keyword class:

Code Block     override func awakeFromNib() {

I do not understand why Xcode points this line with proper diagnostics, you should better send a feedback about this.

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Answer 1

OOPer OP

Dec ’20

Accepted Answer

The problem exists in this line:

Code Block     override class func awakeFromNib() {

The method awakeFromNib() which you want to override is an instance method, not a class method.
Remove the keyword class:

Code Block     override func awakeFromNib() {

I do not understand why Xcode points this line with proper diagnostics, you should better send a feedback about this.

0

Answer 2

LogicalLight OP

Dec ’20

Fascinating, and thank you. The code completion feature offers two variants of awakeFromNib (class and instance) and does not distinguish them. I'll double-check both of these flaws in the latest Xcode and will report them if they're unfixed.

It never occurred to me to notice the class keyword, although I did notice the error using the adjective "instance".

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