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Sunday, January 19, 2025

Utilizing Xcode Previews in UIKit Growth


When SwiftUI was first launched, one of many nice options that piqued my curiosity was the moment preview operate. This function empowers builders to preview the person interface of any view inside Xcode, solely bypassing the necessity for a simulator.

Previous to Xcode 15, the preview function was unique to the SwiftUI framework. Nonetheless, with the newest launch of Xcode, Apple expanded the utility of this function to UIKit as effectively.

On this tutorial, let’s see how one can make use of this preview function when creating UIKit apps.

Utilizing #Preview to Preview View Controllers

To preview a UIKit view or view controller in Xcode, all you must do is about up a preview code block utilizing the #Preview macro. Right here is an instance:

#Preview {
    let vc = ViewController()
    return vc
}

For individuals who have expertise utilizing the #Preview function in SwiftUI, the syntax needs to be fairly acquainted. When you enter the preview code, Xcode exhibits a further pane, offering a preview of your view controller.

uikit-preview-xcode-view-controller

As you modify the code of ViewController, Xcode ought to show the change immediately. For instance, you’ll be able to attempt to modify the code like under:

class ViewController: UIViewController {

    lazy var helloButton: UIButton = {
        let button = UIButton(configuration: .borderedProminent())

        button.setTitle("Howdy", for: .regular)

        let motion = UIAction { motion in
            print("Howdy")

            let alertController = UIAlertController(title: "Howdy", message: "Howdy World", preferredStyle: .alert)
            let alertAction = UIAlertAction(title: "Okay", type: .default)

            alertController.addAction(alertAction)
            self.current(alertController, animated: true)
        }


        button.addAction(motion, for: .touchUpInside)

        button.translatesAutoresizingMaskIntoConstraints = false

        return button
    }()

    override func viewDidLoad() {
        tremendous.viewDidLoad()

        self.view.addSubview(helloButton)

        helloButton.centerXAnchor.constraint(equalTo: view.centerXAnchor, fixed: 0).isActive = true
        helloButton.centerYAnchor.constraint(equalTo: view.centerYAnchor, fixed: 0).isActive = true

    }

}

The preview pane will present a button that claims “Howdy”. Like in SwiftUI growth, you’ll be able to examine the person interface straight within the preview. Should you press the “Howdy” button, a warning or alert will pop up.

Xcode-uikit-preview-button-action

Previewing View Controllers in Interface Builder

The #Preview macro can be used to preview view controllers designed in Interface Builder (or Storyboard). Assuming you’ve created a view controller, configured with a storyboard ID, you’ll be able to write the next code to preview it in Xcode:

#Preview("LoginView") {
    let vc = UIStoryboard(title: "Principal", bundle: nil).instantiateViewController(withIdentifier: "LoginView") as UIViewController

    return vc
}

You employ the instantiateViewController methodology to instantiate the view controller and preview it in Xcode. Optionally, you can provide the preview a reputation (e.g. LoginView).

swiftui-uikit-preview-storyboard

Abstract

With the discharge of Xcode 15, Apple has expanded the moment preview function, beforehand unique to SwiftUI, to UIKit as effectively. Builders can now preview the person interface of any UIKit view or view controller inside Xcode utilizing the #Preview macro, eliminating the necessity for a simulator. This function additionally extends to view controllers designed in Interface Builder or Storyboard. Going ahead, profit from this preview function to expedite your UIKit growth course of.

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