How to open a window in SwiftUI using NSWindowController?

Although many things in SwiftUI are idiomatic and straightforward, showing your view in a new window needs a bit of coding to do. Hence, this short post.

First, let’s create a Window Controller that will hold your window/view:

import AppKit
import SwiftUI

class WindowController<RootView: View>: NSWindowController {
    convenience init(rootView: RootView) {
        let hostingController = NSHostingController(rootView: rootView.frame(width: 400, height: 400))
        let window = NSWindow(contentViewController: hostingController)
        window.setContentSize(NSSize(width: 400, height: 400))
        self.init(window: window)
    }
}

What we’re doing here is creating a Hosting Controller (which is a subclass of View Controller) that takes your supplied View, does its magic, and then gives it to NSWindow.

Now, let’s create two Views in SwiftUI, Parent and Child, like below:

import SwiftUI

struct NewWindowParentView: View {
    @State private var windowCount = 1
    
    var body: some View {
        Button("Show new window") {
            let windowController = WindowController(rootView: NewWindowChildView())
            windowController.window?.title = "Child Window \(windowCount)"
            windowCount += 1
            windowController.showWindow(nil)
        }
    }
}

import SwiftUI

struct NewWindowChildView: View {
    var body: some View {
        Text("Child view")
    }
}

Parent View resemble whatever your main View in your app is and the Child View is the View that you want to show in a new Window.

That’s it. So, when you open the Parent View, you will see a Button and every time you press this button, a new Window will be created showing your Child View.

Lastly, the entire example code can be found on GitHub.

Note: Apple has now added better ways to open windows programmatically in SwiftUI.