iOS - Calling App Delegate method from ViewController

📱📞 Calling App Delegate method from ViewController in iOS - Easy Solutions! 🧩

🤔 Have you ever wondered how to call an App Delegate method from a ViewController in iOS? Maybe you ran into a problem where you needed to trigger a function in a different view controller from a button click, without using Interface Builder (IB)? Well, fret not! In this blog post, we'll explore some easy solutions to this common issue and help you navigate the sometimes tricky world of iOS development. Let's dive in! 🏊‍♂️💥

🚀 The Problem: You want to create a button in code that, when tapped, takes you to a different view controller and triggers a function in that new view controller. You are unable to use IB for this task.

🎯 The Solution: To accomplish this, you can take advantage of the shared instance of the App Delegate and make use of the UIApplication.shared.delegate property. Follow these simple steps:

1️⃣ Step 1: Access the App Delegate instance In your ViewController, import the UIKit framework and declare a property to hold the App Delegate instance:

import UIKit

class MyViewController: UIViewController {
    let appDelegate = UIApplication.shared.delegate as! AppDelegate
    // ...
}

2️⃣ Step 2: Call the App Delegate method Now, you can call any method from the App Delegate by accessing it through the appDelegate property:

appDelegate.myMethod(argument: "Hello!")

3️⃣ Step 3: Implement the required method in the App Delegate In your App Delegate, define the myMethod method to perform the desired functionality:

func myMethod(argument: String) {
    // Do something with the argument
}

🔐 Example Scenario: Let's assume you have two view controllers: SplashViewController and WalkthroughViewController. In SplashViewController, you have buttons for each room, and when a button is tapped, it should navigate to WalkthroughViewController and trigger a function to display the corresponding room walkthrough.

In SplashViewController:

@IBAction func roomButtonTapped(_ sender: UIButton) {
    guard let walkthroughVC = storyboard?.instantiateViewController(withIdentifier: "WalkthroughViewController") as? WalkthroughViewController else {
        return
    }
    appDelegate.navigateToWalkthrough(selectedRoom: sender.tag, walkthroughVC)
}

In the App Delegate:

func navigateToWalkthrough(selectedRoom: Int, _ walkthroughVC: WalkthroughViewController) {
    walkthroughVC.displayRoom(selectedRoom)
    window?.rootViewController = walkthroughVC
    window?.makeKeyAndVisible()
}

🔔 Call-to-Action: Now that you've learned how to call the App Delegate method from a ViewController effortlessly, it's time to put this knowledge into action! Start incorporating this technique into your own projects and let us know how it goes. 🚀😎

Share your experience in the comments below! Have you encountered any other challenges related to iOS development that you'd like us to cover in future blog posts? Let us know! And don't forget to share this post with your fellow developers who might find it helpful. Happy coding! 💻🙌

Disclaimer: The use of "IB" instead of Interface Builder is purely for brevity and familiarity. Please note that Storyboards and Interface Builder are still part of modern iOS development and offer powerful features.

📚 References:

• Apple Developer Documentation - UIApplication.shared

• Medium - How to update the UI in AppDelegate in Swift

• Stack Overflow - Calls to delegate methods from another class

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