How to count number of uicollectionview's rows in swift

Question

I need to determine uicollectionview's height.

let layout = contactCollectionView.collectionViewLayout
let heightSize = String(Int(layout.collectionViewContentSize.height))

The above solution works on some situations in my project. In this specific situation I need to count number of rows and then multiple it with a number to find height.

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        // height = (count rows) * 30 . every cell height is 30 
        // every cell has different width.
        return (presenter?.selectedContact.count)!
    }

How can I find number of rows?

Update

Look at the image.

This is my collectionView. Every cell has different width(because it is string). So It has different rows. The width of this collectionView is width of view.frame

You mean you want to find the scrollable height? Like the size of the whole content? — LinusGeffarth, Jul 25 '17 at 10:04
layout.collectionViewContentSize.height returns zero in this situation. Because the height of my stackView is zero and it can not compute height. I need to count the number rows, then multiple with a number to find whole content size. — Amir Shabani, Jul 25 '17 at 10:10
So you want to know the height it *will* have after returning the 30, right? — LinusGeffarth, Jul 25 '17 at 10:13
Every cell height is 30. if It count rows. I can find height. — Amir Shabani, Jul 25 '17 at 10:18
How are you assigning values/content to the rows in the collectionView ? If you are using an array, you could simply use the count of the array. — Sneha, Jul 25 '17 at 12:01

Matin Kajabadi · Accepted Answer · 2021-06-23T23:36:02.727

You can compare if the collectionView's width is greater than total previous width(s) then you increment rowCounts by one. I am assuming you are implementing UICollectionViewDelegateFlowLayout methods and per each cell you know the dynamic width at the moment. if you won't know the width at that moment, you can also calculate the width of string that would take with considering UIfont along with other stuff in each cell.

Here is a reference how to calculate the width of a string https://stackoverflow.com/a/30450559/6106583

Something like below

//stored properties 
var totalWidthPerRow = CGFloat(0)
var rowCounts = 0   
let spaceBetweenCell = CGFloat(10) // whatever the space between each cell is 


func collectionView(_collectionView:UICollectionView, layoutcollectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
     
   let collectionViewWidth = view.frame.width 
   let dynamicCellWidth = //whatever you calculate the width 
   totalWidthPerRow += dynamicCellWidth + spaceBetweenCell
         

   if (totalWidthPerRow > collectionViewWidth) {
      rowCounts += 1
      totalWidthPerRow = dynamicCellWidth + spaceBetweenCell
   }

  return CGSizeMake(dynamicCellWidth , CGFloat(30))
}

This worked really for me with a few tweaks. Instead of using sizeForItemAt, I performed it in cellForItemAt where I could access each cells text width. I also started the rowCounts = 1, reset rowCounts and totalWidthPerRow when adding or subtracting new cells, and added a heightconstraint outlet from the collectionView which was made equal to rowCounts * rowHeight. Thanks Matt! — Trevor, May 08 '18 at 11:45

How to count number of uicollectionview's rows in swift

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