In the ever-evolving landscape of mobile applications, keeping your app up-to-date is not just a best practice—it’s often a necessity. Whether it’s a critical security patch, a new feature release, or a simple bug fix, ensuring that your users are running the latest version of your app can be crucial for both user experience and security. This is where the concept of “Force Update” comes into play. A Force Update mechanism allows you to compel users to update the app to continue using it. This is particularly useful for critical updates that you can’t afford users to miss.
In this article, we’ll explore how to implement a Force Update mechanism in an iOS app using Combine for the networking layer and SwiftUI for the UI. We’ll start by setting up a publisher in the networking layer that triggers an event when an update is required. Then, we’ll see how to listen for this event in the SwiftUI app to replace the main window with a Force Update screen. Finally, we’ll discuss how to block all further network requests until the app is updated.
Table Of Contents:
- Networking Layer: Setting Up the Publisher with Combine
- SwiftUI App: Listening for Force Update Events
- Testing
- Next Steps
- Conclusion
- Related Articles
Networking Layer: Setting Up the Publisher with Combine
To detect when a Force Update is required, we’ll set up a publisher in the networking layer that listens for a specific trigger from the backend. Once this trigger is received, the publisher will emit an event to notify the app.
import Combine
struct ForceUpdateService {
private var forceUpdatePublisher = PassthroughSubject<Void, Never>()
var forceUpdateReceived: AnyPublisher<Void, Never> {
return forceUpdatePublisher.eraseToAnyPublisher()
}
func checkForForceUpdate() {
// Networking code to check for update from the backend
// If update is required, trigger the publisher
if /* Condition for force update from backend */ {
forceUpdatePublisher.send()
}
}
}
Note: You should somehow send the iOS version used in your app in every request to the backend. So the backend can return whether or not the force_update should be triggered. One of the easiest way to do this, is to send an user_agent header.
SwiftUI App: Listening for Force Update Events
Now that we have our publisher set up, the next step is to listen for these events in the SwiftUI app. When an event is received, we’ll replace the main window of the app with a Force Update screen.
import SwiftUI
@main
struct MyApp: App {
// Note: Maybe the service would be injected into the networking layer, but you get the point.
@StateObject private var forceUpdateService = ForceUpdateService()
@State private var showForceUpdateScreen = false
var body: some Scene {
WindowGroup {
if showForceUpdateScreen {
ForceUpdateScreen()
} else {
ContentView()
}
}
.onReceive(forceUpdateService.forceUpdateReceived) { _ in
showForceUpdateScreen = true
}
}
}
Testing
Testing the publisher is pretty straight-forward:
import XCTest
import Combine
@testable import YourModule
final class ForceUpdateTests: XCTestCase {
private var sut: MyApp!
private var forceUpdateService: ForceUpdateService!
private var cancellables: Set<AnyCancellable>!
override func setUp() {
super.setUp()
forceUpdateService = ForceUpdateService()
sut = MyApp(forceUpdateService: forceUpdateService)
cancellables = []
}
func testShowForceUpdateScreenIsTrueWhenEventReceived() async {
let expectation = XCTestExpectation(description: "showForceUpdateScreen should be true")
forceUpdateService.forceUpdateReceived
.sink { _ in
XCTAssertTrue(self.sut.showForceUpdateScreen)
expectation.fulfill()
}
.store(in: &cancellables)
forceUpdateService.checkForForceUpdate() // Force this method to return the force update error using DI.
await fulfillment(of: [expectation], timeout: 0.5)
}
}
Next Steps
Some things to consider when triggering the ForceUpdate Screen are:
- Make sure the users can’t by pass this screen (check accessibility features).
- Block further requests to the backend.
- Check the memory graph to make sure everything is released from memory correctly.
Conclusion
Implementing a Force Update mechanism is a critical aspect of maintaining a secure and up-to-date app. By leveraging Combine and SwiftUI, you can create a seamless experience for your users, ensuring they are always running the latest version of your app.