How to make a simple collection view with Swift

Question

This project has been tested with Xcode 10 and Swift 4.2.

Create a new project

It can be just a Single View App.

Add the code

Create a new Cocoa Touch Class file (File > New > File... > iOS > Cocoa Touch Class). Name it MyCollectionViewCell. This class will hold the outlets for the views that you add to your cell in the storyboard.

import UIKit
class MyCollectionViewCell: UICollectionViewCell {
    
    @IBOutlet weak var myLabel: UILabel!
}

We will connect this outlet later.

Open ViewController.swift and make sure you have the following content:

import UIKit
class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
    
    let reuseIdentifier = "cell" // also enter this string as the cell identifier in the storyboard
    var items = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "40", "41", "42", "43", "44", "45", "46", "47", "48"]
    
    
    // MARK: - UICollectionViewDataSource protocol
    
    // tell the collection view how many cells to make
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.items.count
    }
    
    // make a cell for each cell index path
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        
        // get a reference to our storyboard cell
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! MyCollectionViewCell
        
        // Use the outlet in our custom class to get a reference to the UILabel in the cell
        cell.myLabel.text = self.items[indexPath.row] // The row value is the same as the index of the desired text within the array.
        cell.backgroundColor = UIColor.cyan // make cell more visible in our example project
        
        return cell
    }
    
    // MARK: - UICollectionViewDelegate protocol
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        // handle tap events
        print("You selected cell #\(indexPath.item)!")
    }
}

Notes

• UICollectionViewDataSource and UICollectionViewDelegate are the protocols that the collection view follows. You could also add the UICollectionViewFlowLayout protocol to change the size of the views programmatically, but it isn't necessary.
• We are just putting simple strings in our grid, but you could certainly do images later.

Set up the storyboard

Drag a Collection View to the View Controller in your storyboard. You can add constraints to make it fill the parent view if you like.

Make sure that your defaults in the Attribute Inspector are also

• Items: 1
• Layout: Flow

The little box in the top left of the Collection View is a Collection View Cell. We will use it as our prototype cell. Drag a Label into the cell and center it. You can resize the cell borders and add constraints to center the Label if you like.

Write "cell" (without quotes) in the Identifier box of the Attributes Inspector for the Collection View Cell. Note that this is the same value as let reuseIdentifier = "cell" in ViewController.swift.

And in the Identity Inspector for the cell, set the class name to MyCollectionViewCell, our custom class that we made.

Hook up the outlets

• Hook the Label in the collection cell to myLabel in the MyCollectionViewCell class. (You can Control-drag.)
• Hook the Collection View delegate and dataSource to the View Controller. (Right click Collection View in the Document Outline. Then click and drag the plus arrow up to the View Controller.)

Finished

Here is what it looks like after adding constraints to center the Label in the cell and pinning the Collection View to the walls of the parent.

Making Improvements

The example above works but it is rather ugly. Here are a few things you can play with:

Background color

In the Interface Builder, go to your Collection View > Attributes Inspector > View > Background.

Cell spacing

Changing the minimum spacing between cells to a smaller value makes it look better. In the Interface Builder, go to your Collection View > Size Inspector > Min Spacing and make the values smaller. "For cells" is the horizontal distance and "For lines" is the vertical distance.

Cell shape

If you want rounded corners, a border, and the like, you can play around with the cell layer. Here is some sample code. You would put it directly after cell.backgroundColor = UIColor.cyan in code above.

cell.layer.borderColor = UIColor.black.cgColor
cell.layer.borderWidth = 1
cell.layer.cornerRadius = 8

See this answer for other things you can do with the layer (shadow, for example).

Changing the color when tapped

It makes for a better user experience when the cells respond visually to taps. One way to achieve this is to change the background color while the cell is being touched. To do that, add the following two methods to your ViewController class:

// change background color when user touches cell
func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath)
    cell?.backgroundColor = UIColor.red
}

// change background color back when user releases touch
func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath)
    cell?.backgroundColor = UIColor.cyan
}

Here is the updated look:

Further study

• A Simple UICollectionView Tutorial
• UICollectionView Tutorial Part 1: Getting Started
• UICollectionView Tutorial Part 2: Reusable Views and Cell Selection

UITableView version of this Q&A

• UITableView example for Swift

For swift 4.2 --

//MARK: UICollectionViewDataSource

func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
    return 1     //return number of sections in collection view
}

func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 10    //return number of rows in section
}

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCell", for: indexPath as IndexPath)
    configureCell(cell: cell, forItemAtIndexPath: indexPath)
    return cell      //return your cell
}

func configureCell(cell: UICollectionViewCell, forItemAtIndexPath: NSIndexPath) {
    cell.backgroundColor = UIColor.black


    //Customise your cell

}

func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {
    let view =  collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "collectionCell", for: indexPath as IndexPath) as UICollectionReusableView
    return view
}

//MARK: UICollectionViewDelegate
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    // When user selects the cell
}

func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
    // When user deselects the cell
}

Delegates and Datasources of UICollectionView

//MARK: UICollectionViewDataSource

override func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
    return 1     //return number of sections in collection view
}

override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 10    //return number of rows in section
}

override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("collectionCell", forIndexPath: indexPath)
    configureCell(cell, forItemAtIndexPath: indexPath)
    return cell      //return your cell
}

func configureCell(cell: UICollectionViewCell, forItemAtIndexPath: NSIndexPath) {
    cell.backgroundColor = UIColor.blackColor()


    //Customise your cell

}

override func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {
    let view =  collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionHeader, withReuseIdentifier: "collectionCell", forIndexPath: indexPath) as UICollectionReusableView
    return view
}

//MARK: UICollectionViewDelegate
override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
      // When user selects the cell
}

override func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
     // When user deselects the cell
}

UICollectionView implementation is quite interesting. You can use the simple source code and watch a video tutorial using these links :

https://github.com/Ady901/Demo02CollectionView.git

https://www.youtube.com/watch?v=5SrgvZF67Yw

extension ViewController : UICollectionViewDataSource {

    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 2
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return nameArr.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "DummyCollectionCell", for: indexPath) as! DummyCollectionCell
        cell.titleLabel.text = nameArr[indexPath.row]
        cell.userImageView.backgroundColor = .blue
        return cell
    }

}

extension ViewController : UICollectionViewDelegate {

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        let alert = UIAlertController(title: "Hi", message: "\(nameArr[indexPath.row])", preferredStyle: .alert)
        let action = UIAlertAction(title: "OK", style: .default, handler: nil)
        alert.addAction(action)
        self.present(alert, animated: true, completion: nil)
    }

}