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More details can be found on the related blog post at the Always Right Institute.

At WWDC 2019 Apple announced SwiftUI. A single "cross platform", "declarative" framework used to build tvOS, macOS, watchOS and iOS UIs. SwiftWebUI is bringing that to the Web ✔️

Disclaimer: This is a toy project! Do not use for production. Use it to learn more about SwiftUI and its inner workings.

So what exactly is SwiftWebUI? It allows you to write SwiftUI Views which display in a web browser:

import SwiftWebUI

struct MainPage: View {
  @State var counter = 0
  
  func countUp() { 
    counter += 1 
  }
  
  var body: some View {
    VStack {
      Text("🥑🍞 #\(counter)")
        .padding(.all)
        .background(.green, cornerRadius: 12)
        .foregroundColor(.white)
        .onTapGesture(self.countUp)
    }
  }
}

Results in:

Unlike some other efforts this doesn't just render SwiftUI Views as HTML. It also sets up a connection between the browser and the code hosted in the Swift server, allowing for interaction - buttons, pickers, steppers, lists, navigation, you get it all!

In other words: SwiftWebUI is an implementation of (many but not all parts of) the SwiftUI API for the browser.

To repeat the Disclaimer: This is a toy project! Do not use for production. Use it to learn more about SwiftUI and its inner workings.

Update 2019-07-08: There are three options to run SwiftWebUI:

One can use a macOS Catalina installation to run SwiftWebUI. Make sure that the Catalina version matches your Xcode 11 beta! (“Swift ABI” 🤦‍♀️)

Fortunately it is really easy to install Catalina on a separate APFS volume. And an installation of Xcode 11 is required to get the new Swift 5.1 features SwiftUI makes heavy use of. Got that? Very well!

Why is Catalina required? SwiftUI makes use of new Swift 5.1 runtime features (e.g. opaque result types). Those features are not available in the Swift 5 runtime that ships with Mojave. (another reason is the use of Combine which is only available in Catalina, though that part could be fixed using OpenCombine)

SwiftWebUI now runs on Linux using OpenCombine (also works without that, but then some things don't work, e.g. NavigationView).

A Swift 5.1 snapshot is required. We also provide a Docker image containing a 5.1 snapshot over here: helje5/swift.

The Xcode 11beta iOS 13 simulators do run on Mojave. You might be able to run SwiftWebUI within an iOS app.

To setup a SwiftWebUI project, create a "macOS tool project" in Xcode 11, then use the new SwiftPM integration and add https://github.com/SwiftWebUI/SwiftWebUI as a dependency.

Open the main.swift file and replace it's content with:

import SwiftWebUI

SwiftWebUI.serve(Text("Holy Cow!"))

Compile and run the app in Xcode, open Safari and hit http://localhost:1337/:

A small SwiftWebUI sample based on the SwiftUI Essentials "Avocado Toast App". Find it over here: AvocadoToast.

Brought to you by The Always Right Institute and ZeeZide. We like feedback, GitHub stars, cool contract work, presumably any form of praise you can think of.