Swift 40

One of the best features for developers that came in the iOS 6 SDK is UICollectionView. It’s been a popular tool for developers since, so let’s review how to create one in Swift (if you need it in objective-c read Tutorial: Collection View using Flow Layout).

UICollectionView is very similar to UITableView but you can customize it a lot more and it can scroll horizontal, goodbye scroll views! Most recently I used a collection view for a bottom navigation scroller and it worked really well.

A UICollectionView view has three main components:
1. Cells: Display your content in cells that are de-queued as they leave the screen.
2. Supplementary Views: Add labels, section headers and footers to define your content areas.
3. Decoration Views: Decorate the collection view to look like a bookshelf or a background image.

Start by adding the delegates to your class file and define your collection view.

class ViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
    
    @IBOutlet var collectionView: UICollectionView?

The most common layout for a UICollectionView is UICollectionViewFlowLayout. Flow layout organizes items into a grid with optional header and footer views for each section. The items in the collection view flow from one row or column (depending on the scrolling direction) to the next, with each row comprising as many cells as will fit. Cells can be the same sizes or different sizes.

Define the UICollectionView & UICollectionViewFlowLayout properties in the viewDidLoad method.

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: 20, left: 10, bottom: 10, right: 10)
    layout.itemSize = CGSize(width: 90, height: 90)
    collectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
    collectionView!.dataSource = self
    collectionView!.delegate = self
    collectionView!.registerClass(CollectionViewCell.self, forCellWithReuseIdentifier: "CollectionViewCell")
    collectionView!.backgroundColor = UIColor.whiteColor()
    self.view.addSubview(collectionView!)
}

Most of the properties are self explanatory but the key is to define your cell class if you are using custom cells (just like table views) and setting the size of the cells, above they are set to 90×90. Choose your section insets which is the spacing in between each cell, I have it set to 20 for the top and 10 for the rest. Lastly define the layout, we’re using let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout().

Setting up a UICollectionView is very similar to a UITableView, so you’ll recognized a lot of the methods below.

func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
    return 1
}

func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 20
}

Above we’re defining how many items and sections are in the collection view. If you have more than one section, then you’ll need to define the number of sections, if you only have one you don’t need that method.

Below is the real meat of the UICollectionView, defining the cells with your data. If you choose to use a custom cell you can add images or whatever you need to display.

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("CollectionViewCell", forIndexPath: indexPath) as CollectionViewCell
    cell.backgroundColor = UIColor.blackColor()
    cell.textLabel?.text = "\(indexPath.section):\(indexPath.row)"
    cell.imageView?.image = UIImage(named: "circle")
    return cell
}

Finally you can drag the UICollectionView object into your view within your NIB or storyboard. Move and scale the collection view to where you want to display it and review all of the properties within the inspector. Be sure to hookup the collectionView reference outlet and dataSource and delegates so the collection view can provide all the functionality available. Do the same for the Collection View Flow Layout. (See image on the right).

You can grab the full source code for this tutorial. Note: Built for XCode6-Beta7.
If you need it built using Xcode 6.3 (Swift 1.2).

Sometimes you need all users to use the same version of your App. There are many reasons for this but the most popular is to ensure all users have a specific new feature that’s only available in the latest version. Another popular reason is you changed a data source or functionality that is no longer supported in older versions of your app. This will force the user to upgrade the app on their device and will not allow them to use their current version anymore.

It’s important that this feature is built into your very first release of your application (v1.0) so you can force all users to upgrade when you need to.

Below is a tutorial to help you add a forced upgrade alert in Swift.

Web Server API

1. Create “appVersion.php” on your Server. This can be created using any kind of Web API (Perl, PHP, Ruby, etc..).
2. Write this code into your file. This code will give out your latest App Version.

Get App Version using NSURLConnection

1. You’ll need the following method to read in the latest App Version from the Web Server API.

   func getAppVersion() {
       let url = NSURL(string:"http://www.brianjcoleman.com/code/appVersion.php")
       let cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringLocalCacheData
       var request = NSMutableURLRequest(URL: url!, cachePolicy: cachePolicy, timeoutInterval: 2.0)
       request.HTTPMethod = "POST"
       
       // set Content-Type in HTTP header
       let boundaryConstant = "----------V2ymHFg03esomerandomstuffhbqgZCaKO6jy";
       let contentType = "multipart/form-data; boundary=" + boundaryConstant
       NSURLProtocol.setProperty(contentType, forKey: "Content-Type", inRequest: request)
       
       // set data
       var dataString = ""
       let requestBodyData = (dataString as NSString).dataUsingEncoding(NSUTF8StringEncoding)
       request.HTTPBody = requestBodyData
       //println("Data String: \(dataString)")
       // set content length
       //NSURLProtocol.setProperty(requestBodyData.length, forKey: "Content-Length", inRequest: request)
       
       var response: NSURLResponse? = nil
       var error: NSError? = nil
       let reply = NSURLConnection.sendSynchronousRequest(request, returningResponse:&response, error:&error)
       
       let results = NSString(data:reply!, encoding:NSUTF8StringEncoding)
       println("API Response: \(results)")
       self.serverAppVersion = results!
   }
   

Display UIAlertController in Swift

1. Then you need to compare the minimum app version from the web server against the app version the user has on their device.
2. If the minimum app version from the server is greater than the users app version it will display an alert view and force the user to upgrade.
3. Add the method below into your first view controller in your app.

   func checkForAppUpdate() {
       
       getAppVersion()
       
       var minAppVersion = self.serverAppVersion
       var appVersion = NSBundle.mainBundle().objectForInfoDictionaryKey("CFBundleShortVersionString") as String
       
       println("Current Version: \(appVersion) -- Minimum Version: \(minAppVersion)")
       
       //Compare App Versions
       var minAppVersionComponents : NSArray = minAppVersion.componentsSeparatedByString(".")
       var appVersionComponents : NSArray = appVersion.componentsSeparatedByString(".")
       
       var needToUpdate = false
       
       for i in 0..
   Lastly you'll need to call the checkForAppUpdate() from viewDidLoad() so it will only get called the when the app is initially loaded.
   

You can grab the full source code for this tutorial. Note: Built using XCode6.1
If you need it built using Xcode 6.3 (Swift 1.2).