A basic understanding of Swift and Node.js is needed to follow this tutorial. One of the most common elements on applications (web or otherwise) is counters. YouTube, for instance, uses counters to see how many people have viewed a particular video. Facebook also does the same for videos on their platform. Most of the counters on these sites, however, only update the count when you have refreshed the page. This leaves a lot to be desired, as sometimes you just want to see the number increase in realtime. This gives you the impression that the item is being viewed by many people at the moment. In this article, we are going to explore how we can leverage the realtime nature of Pusher to create a counter that updates in realtime. We will be creating a video viewer iOS application with a realtime counter showing how many people have viewed the video. To follow along, you will need basic knowledge of Swift, Xcode and command line. You will also need to set up a Pusher account and create an application. You can do so . here Basic setup To get started you will need Cocoapods installed on your machine. Cocoapods is a package manager and we will be using this to manage the dependencies on the application. To install Cocoapods, type this in your command line: $ gem install cocoapods After you are done installing that, launch Xcode and create a new single page application project. Follow the setup wizard, and then once the Xcode project editor is open, close Xcode. to the root directory of your project and run the command: cd $ pod init This should create a in the root of your project. Open this file in your favorite editor and then update the contents of the file to the following: Podfile # Uncomment the next line to define a global platform for your projectplatform :ios, '9.0' target 'counter' do Comment the next line if you're not using Swift and don't want to use dynamic frameworks use_frameworks! Pods for counter pod 'Alamofire'pod 'PusherSwift' end In the file above we have specified two dependencies: and . These will be useful later in the project. Now install these dependencies by running this command from your terminal: PusherSwift Alamofire $ pod install Once this is complete, you should have a file in the root directory of your project. Open this file and it should launch Xcode. (Make sure you don't have any instance of Xcode running for this project before opening the file or you will get an error.) .xcworkspace Creating the views for our realtime application Now that the project is open, we will create some views for our application. Open the file and in there we will create the views. Main.storyboard We want to create a navigation controller that will have a as the root controller of the navigation controller. Then in the new view controller, we will add a webview; this is where we will be embedding the video we want people to view. We will also add two labels, one for the counter and the other will just be a plain immutable message. ViewController After we are done, this is what we have so far: Adding our realtime feature to our application Now that we have created the application, we can now add the code that will interact with the views and add the realtime support and the video also. Create a new class and link it to the view controller we created above. Then create a split view in Xcode and ctrl+drag from the to the view controller. This should create an in the controller; do the same for the counter label so it creates another . Our controller should now have two s one for the webview and one for the counter label. Great. MainViewController webview @IBOutlet @IBOutlet @IBOutlet Now we are going to add the code to load our video. We are going to be using a YouTube video of a Pusher tutorial for this exercise. In the method add the following: viewDidLoad func viewDidLoad() {super.viewDidLoad()loadYoutube(videoID:"xDQ8vzD0lzw")} Now let's create the method and the other dependent methods: loadYoutube func loadYoutube(videoID:String) {self.automaticallyAdjustsScrollViewInsets = falsewebview.allowsInlineMediaPlayback = truewebview.mediaPlaybackRequiresUserAction = false let embedHTML = getEmbedHTML(id:videoID);

let url: NSURL = NSURL(string: "[https://www.youtube.com/embed/\\(videoID)](https://www.youtube.com/embed/%5C%28videoID%29)")!

webview.loadHTMLString(embedHTML as String, baseURL:url as URL ) } private func getEmbedHTML(id: String) -> String {return "<html><head><style type=\"text/css\">body {background-color: transparent;color: white;}</style></head><body style=\"margin:0\"> <iframe webkit-playsinline width=\"100%\" height=\"100%\" src=\" " frameborder=\"0\"></iframe>";} https://www.youtube.com/embed/\(id)?feature=player_detailpage&playsinline=1\ Now we have instructed the application to load a YouTube video automatically. However, the counter functionality does not yet work. Let’s fix that. Import the library and add a new method to update the counter using Pusher: PusherSwift updateViewCount() {let options = PusherClientOptions(host: .cluster("PUSHER_CLUSTER")) pusher = Pusher(key: "PUSHER\_KEY", options: options)

let channel = pusher.subscribe("counter")  
let \_ = channel.bind(eventName: "new\_user", callback: { (data: Any?) -> Void in  
    if let data = data as? \[String: AnyObject\] {  
        let viewCount = data\["count"\] as! NSNumber  
        self.count.text = "\\(viewCount)" as String!  
    }  
})

pusher.connect() } Note: Where it says _PUSHER_CLUSTER_ and _PUSHER_KEY_ , you should replace with your actual Pusher cluster and key. You'll also need to import Now you can just call the from the method so it is called when the view is loaded. updateViewCount viewDidLoad One final thing we will do is use to send a request to a backend so the counter can be updated and saved, so we do not lose the count of people who have viewed the video. Import and add the following: Alamofire Alamofire func sendViewCount() {Alamofire.request(endpoint, method: .post).validate().responseJSON { response inswitch response.result {case .success:if let result = response.result.value {let data = result as! NSDictionarylet viewCount = data["count"] as! NSNumberself.count.text = "\(viewCount)" as String!}case .failure(let error):print(error)}}} Now that we are done with that, the should now look a little like this: MainViewController import UIKitimport Alamofireimport PusherSwift class MainViewController: UIViewController { [@IBOutlet](http://twitter.com/IBOutlet "Twitter profile for @IBOutlet") weak var count: UILabel!  
[@IBOutlet](http://twitter.com/IBOutlet "Twitter profile for @IBOutlet") weak var webview: UIWebView!

var endpoint: String = "[http://localhost:4000/update\_counter](http://localhost:4000/update_counter)"

var pusher : Pusher!

override func viewDidLoad() {  
    super.viewDidLoad()  
    loadYoutube(videoID:"xDQ8vzD0lzw")  
    sendViewCount()  
    updateViewCount()  
}

func sendViewCount() {  
    Alamofire.request(endpoint, method: .post).validate().responseJSON { response in  
        switch response.result {

        case .success:  
            if let result = response.result.value {  
                let data = result as! NSDictionary  
                let viewCount = data\["count"\] as! NSNumber  
                self.count.text = "\\(viewCount)" as String!  
            }  
        case .failure(let error):  
            print(error)  
        }  
    }  
}

func updateViewCount() {  
    let options = PusherClientOptions(  
        host: .cluster("PUSHER\_CLUSTER")  
    )

    pusher = Pusher(key: "PUSHER\_KEY", options: options)

    let channel = pusher.subscribe("counter")  
    let \_ = channel.bind(eventName: "new\_user", callback: { (data: Any?) -> Void in  
        if let data = data as? \[String: AnyObject\] {  
            let viewCount = data\["count"\] as! NSNumber  
            self.count.text = "\\(viewCount)" as String!  
        }  
    })

    pusher.connect()  
}

func loadYoutube(videoID:String) {  
    self.automaticallyAdjustsScrollViewInsets = false  
    webview.allowsInlineMediaPlayback = true  
    webview.mediaPlaybackRequiresUserAction = false  
    let embedHTML = getEmbedHTML(id:videoID);

    let url: NSURL = NSURL(string: "[https://www.youtube.com/embed/\\(videoID)](https://www.youtube.com/embed/%5C%28videoID%29)")!  
    webview.loadHTMLString(embedHTML as String, baseURL:url as URL )  
}

private func getEmbedHTML(id: String) -> String {  
    return "<html><head><style type=\\"text/css\\">body {background-color: transparent;color: white;}</style></head><body style=\\"margin:0\\"> <iframe webkit-playsinline width=\\"100%\\" height=\\"100%\\" src=\\"[https://www.youtube.com/embed/\\(id)?feature=player\_detailpage&playsinline=1\\](https://www.youtube.com/embed/%5C%28id%29?feature=player_detailpage&playsinline=1%5C)" frameborder=\\"0\\"></iframe>";  
} } If we load the application now, it would load the video but the counter will not work. This is because we have not yet set up a backend logic. Creating the backend for our realtime counter iOS application For the backend, we will be creating a very basic Node.js application. This application will simply have one endpoint that saves the counter state and sends a trigger to Pusher so other listeners subscribed to the channel event can pick it up and update in realtime. To start, create a new directory for your application. In the application create two files: File: package.json {"main": "index.js","dependencies": {"body-parser": "^1.16.0","express": "^4.14.1","pusher": "^1.5.1"}} File: index.js var Pusher = require('pusher');let express = require('express');let bodyParser = require('body-parser');let fs = require('fs'); let app = express(); let pusher = new Pusher({appId: 'PUSHER_ID',key: 'PUSHER_KEY',secret: 'PUSHER_SECRET',cluster: 'PUSHER_CLUSTER',encrypted: true}); app.use(bodyParser.json());app.use(bodyParser.urlencoded({ extended: false })); app.post('/update_counter', function(req, res) {let counterFile = './count.txt'; fs.readFile(counterFile, 'utf-8', function(err, count) {count = parseInt(count) + 1;fs.writeFile(counterFile, count, function (err) {pusher.trigger('counter', 'new_user', {count:count});res.json({count:count});});});}); app.use(function(req, res, next) {let err = new Error('Not Found');err.status = 404;next(err);}); module.exports = app; app.listen(4000, function(){console.log('App listening on port 4000!')}) Finally, create the file in the same directory and chmod it to be writable. counter.txt $ echo "0" > count.txt$ chmod 0644 count.txt Now run to install all the dependencies that node needs to make the backend application work. When the dependencies are done installing, run to start your application. npm install node index.js One last change we would need to make to allow our application interact with the localhost application is in our projects file. Make the changes below before launching the application: info.plist Now, when you launch the application you can see the counter increase, and if there is another instance of the application, they can see the counter increase in realtime. Neat! Conclusion In this article, we explored how you can create realtime counters using Pusher in your iOS applications. We are curious to see how you would incorporate this into your iOS application. If you have any other use cases you would like to see, or have any feedback, leave a comment below. This post first appeared on the . Pusher blog

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