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HomeiOS DevelopmentConstructing a QR Code Scanner App in SwiftUI

Constructing a QR Code Scanner App in SwiftUI

So, what’s QR code? I imagine most of you already know what a QR code is. In case you haven’t heard of it, simply check out the above picture – that’s a QR code.

QR (brief for Fast Response) code is a type of two-dimensional bar code developed by Denso. Initially designed for monitoring elements in manufacturing, QR code has gained recognition in shopper house lately as a approach to encode the URL of a touchdown web page or advertising data. Not like the essential barcode that you just’re accustomed to, a QR code comprises data in each the horizontal and vertical course. Thus, this contributes to its functionality of storing a bigger quantity of information in each numeric and letter kind. I don’t wish to go into the technical particulars of the QR code right here. For those who’re fascinated by studying extra, you possibly can try the official web site of QR code.

As an iOS developer, chances are you’ll surprise how one can empower your app to learn a QR code. Earlier, I’ve written a tutorial on constructing a QR Code reader utilizing UIKit and AVFoundation. With the discharge of SwiftUI, let’s see how the identical QR Code Scanner app may be carried out utilizing this new UI framework.

Take a Fast Have a look at the QR Code Scanner App

The demo app that we’re going to construct is pretty easy and simple. Earlier than we proceed to construct the demo app, nevertheless, it’s vital to know that every one kinds of barcode scanning in iOS, together with QR code scanning, is completely primarily based on video seize. Hold this level in thoughts, because it’ll assist you to perceive this tutorial.

So, how does the demo app work?

Check out the screenshot beneath. That is how the app UI seems to be. The app works just about like a video capturing app however with out the recording characteristic. When the app is launched, it makes use of the iPhone’s rear digital camera to identify a QR code and decodes it robotically. The decoded data (e.g. an URL) is displayed proper on the backside of the display.

QR Code Reader app for demo purpose

Now that you just perceive how the demo app works, let’s get began and develop the QR code reader app in SwiftUI.

Constructing the QRScannerController Class

The SwiftUI framework doesn’t include a built-in API for launching the digital camera. To make use of the gadget’s digital camera, we have to use UIKit to construct a view controller for capturing movies. After which we make use of UIViewControllerRepresentable so as to add the view controller to the SwiftUI challenge.

Assuming you’ve created a brand new SwiftUI challenge in Xcode, let’s first create a brand new Swift file named QRScanner.swift. Within the file, import each SwiftUI and AVFoundation frameworks:

Subsequent, implement a brand new class known as QRScannerController like this:

For those who’ve learn the earlier tutorial, you must perceive how the code works. Anyway, let me rapidly stroll you thru the code once more. As talked about within the earlier part, QR code scanning relies on video seize. To carry out a real-time seize, all we have to do is:

  1. Lookup the again digital camera gadget.
  2. Set the enter of the AVCaptureSession object to the suitable AVCaptureDevice for video capturing.

So, within the viewDidLoad methodology, we initialize the again digital camera utilizing AVCaptureDevice. Subsequent, we create an occasion of AVCaptureDeviceInput utilizing the digital camera gadget. The enter gadget is then added to the captureSession object. An occasion of AVCaptureMetadataOutput is created and added to the identical session object as an output to the seize session.

We additionally set the delegate object (AVCaptureMetadataOutputObjectsDelegate) for processing the QR code. When QR codes are captured from the receiver’s connection, they’re vended to the delegate object. We haven’t carried out this delegate object but and can do it later.

The metadataObjectTypes property is used to specify what sort of metadata we’re fascinated by. The worth of .qr clearly signifies that we simply wish to do QR code scanning.

The previous couple of traces of the code above is to create the video preview layer and add it as a sublayer to the viewPreview view’s layer. This shows the video captured by the gadget’s digital camera on display.

Integrating QRScannerController with SwiftUI

Now that we’ve ready the view controller for capturing video and scanning QR code, how can we combine it with our SwiftUI challenge. SwiftUI supplies a protocol known as UIViewControllerRepresentable to create and handle a UIViewController object.

In the identical file, let’s create a struct named QRScanner that adopts the protocol:

We implement the 2 required strategies of the UIViewControllerRepresentable protocol. Within the makeUIViewController methodology, we return an occasion of QRScannerController. Since we don’t must replace the state of the view controller, the updateUIViewController methodology is empty.

That is how you utilize a UIViewController object in SwiftUI challenge.

Utilizing QRScanner

Now let’s change over to ContentView.swift and use the QRScanner struct we simply created. All you have to initialize within the physique a part of ContentView:

I additionally added a textual content label for displaying the results of QR scan. Within the simulator, it solely shows the textual content label. Later, if you happen to run the app in an actual gadget (iPhone/iPad), the app ought to begin the built-in digital camera.

Earlier than you possibly can efficiently launch the app, you must add a key named NSCameraUsageDescription within the Data.plist file. Within the challenge navigator, choose the challenge file and go to the Data part. Add a brand new row and set the important thing to Privateness – Digital camera Utilization Description. For its worth, set it to We have to entry your digital camera for scanning QR code.

info plist for SwiftUI project

For those who run the app now, it ought to robotically entry the built-in digital camera and begin capturing video. Nonetheless, the QR code scanning doesn’t work but.

Dealing with Scan Outcomes

In ContentView, now we have a state variable to retailer the scan outcome. The query is how can the QRScanner (or QRScannerController) go the decoded data of the QR code again to ContentView?

If you’re not forgetful, we haven’t carried out the delegate (i.e. the occasion of AVCaptureMetadataOutputObjectsDelegate) for processing the QR code. The next delegate methodology of AVCaptureMetadataOutputObjectsDelegate is required to be carried out:

The duty of this delegate is to retrieve the decoded data and go it again to the SwiftUI app. To change information between the view controller object and the SwiftUI interface, we have to present a Coordinator occasion, which additionally adopts the AVCaptureMetadataOutputObjectsDelegate protocol, to deal with these interactions.

First, declare a binding in QRScanner:

Subsequent, insert the next code in QRScanner to arrange the Coordinator class:

The category has a binding for updating the scan outcome. That is how we go the scan outcome again to the SwiftUI objects.

To course of the scan results of QR codes, we additionally implement the metadataOutput methodology. The second parameter (i.e. metadataObjects) of the tactic is an array object, which comprises all of the metadata objects which were learn. The very very first thing we have to do is ensure that this array shouldn’t be nil, and it comprises not less than one object. In any other case, we set the worth of scanResult to No QR code detected.

If a metadata object is discovered, we test to see if it’s a QR code and decode the embedded information. The decoded data may be accessed by utilizing the stringValue property of an AVMetadataMachineReadableCode object.

As soon as we put together the Coordinator class, insert the next methodology to create the Coordinator occasion in QRScanner:

Additionally, replace the makeUIViewController methodology like beneath. Now we have to assign the coordinator object to the controller’s delegate:

The challenge is sort of full. Now change again to ContentView.swift. Replace QRScanner() like beneath to go the scan outcome:

That’s it! You’re able to go! Hit the Run button to compile and take a look at the app on an actual gadget.



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