Custom cell width for one collectionView - ios

Question

I have 3 collectionViews in one view controller. One has all cells of the same width and does not change. The other I would like to set the cell width in code using a constant. The last will calculate its cell's width based on the previous constant and other factors in a custom flow layout.
I tried
extension YourViewController: UICollectionViewDelegate,UICollectionViewDataSource,UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
if collectionView == neededCollectionView {
return CGSize(width: constantWidth, height: constHeight)
} else {
// here ignore all the others and tell them to get this size as usual
}
}
}
but this seems to modify the width for all the collection views .. How do I get this two ignore the 2 collection views that have their size calculated somewhere else

Answer 1

in this function you can't ignore,
you need to return
CGSize
always.
try a break point and check if it gets into the else closure if so
you could try to add this line,
return CGSize(width: yourDefualtWidthConst, height:yourDefualtHeightconst)
or this
return collectionView.itemSize

Answer 2

You have Two options
FIRST OPTION : Return the estimatedItemSize of each CollectionViewCell
1. Get an IBOutlet Reference from each CollectionViewFlowLayout
#IBOutlet weak var firstFlowLayout: UICollectionViewFlowLayout!
2. Add UICollectionViewDelegateFlowLayout delegate in your viewController
3. Implement the delegate method
func collectionView( _ collectionView: UICollectionView,layoutcollectionViewLayout: UICollectionViewLayout,sizeForItemAtindexPath: IndexPath) -> CGSize {
if collectionView.tag == 1 {
return CGSize(width: constantWidth, height: constHeight)
} elseIf collectionView.tag == 2 {
return firstFlowLayout.estimatedItemSize
}
}
SECOND OPTION : Adepter Design pattern
You can also use adapter class for each collectionview and each adapter has a different implementation to resolve this like this
https://stackoverflow.com/a/50920915/5233180
NOT : This implementation for TableView you can make it for collectionview