Find out how to construct macOS apps utilizing solely the Swift Bundle Supervisor?

Swift scripts and macOS apps

Swift compiler 101, you may create, construct and run a Swift file utilizing the swiftc command. Contemplate the most straightforward Swift program that we are able to all think about in a important.swift file:

print("Good day world!")

In Swift if we need to print one thing, we do not even must import the Basis framework, we are able to merely compile and run this piece of code by working the next:

swiftc important.swift   # compile important.swift
chmod +x important       # add the executable permission
./important          # run the binary

The excellent news that we are able to take this one step additional by auto-invoking the Swift compiler below the hood with a shebang).

#! /usr/bin/swift

print("Good day world!")

Now in case you merely run the ./important.swift file it’s going to print out the well-known “Good day world!” textual content. 👋

Due to the program-loader mechanism and naturally the Swift interpreter we are able to skip an additional step and run our single-source Swift code as straightforward as a daily shell script. The excellent news is that we are able to import all form of system frameworks which might be a part of the Swift toolchain. With the assistance of Basis we are able to construct fairly helpful or utterly ineffective command line utilities.

#!/usr/bin/env swift

import Basis
import Dispatch

guard CommandLine.arguments.rely == 2 else {
    fatalError("Invalid arguments")
}
let urlString =  CommandLine.arguments[1]
guard let url = URL(string: urlString) else {
    fatalError("Invalid URL")   
}

struct Todo: Codable {
    let title: String
    let accomplished: Bool
}

let activity = URLSession.shared.dataTask(with: url) { information, response, error in 
    if let error = error {
        fatalError("Error: (error.localizedDescription)")
    }
    guard let response = response as? HTTPURLResponse, response.statusCode == 200 else {
        fatalError("Error: invalid HTTP response code")
    }
    guard let information = information else {
        fatalError("Error: lacking response information")
    }

    do {
        let decoder = JSONDecoder()
        let todos = strive decoder.decode([Todo].self, from: information)
        print("Checklist of todos:")
        print(todos.map { " - [" + ($0.completed ? "✅" : "❌") + "] ($0.title)" }.joined(separator: "n"))
        exit(0)
    }
    catch {
        fatalError("Error: (error.localizedDescription)")
    }
}
activity.resume()
dispatchMain()

Should you name this instance with a URL that may return an inventory of todos it’s going to print a pleasant checklist of the gadgets.

./important.swift https://jsonplaceholder.typicode.com/todos

Sure, you may say that this script is totally ineffective, however for my part it is a tremendous demo app, because it covers how you can examine command line arguments (CommandLine.arguments), it additionally reveals you how you can wait (dispatchMain) for an async activity, reminiscent of a HTTP name by the community utilizing the URLSession API to complete and exit utilizing the appropriate technique when one thing fails (fatalError) or in case you attain the top of execution (exit(0)). Only a few traces of code, however it incorporates a lot information.

Have you ever observed the brand new shebang? If in case you have a number of Swift variations put in in your system, you need to use the env shebang to go along with the primary one which’s accessible in your PATH.

It isn’t simply Basis, however you may import AppKit and even SwiftUI. Properly, not below Linux after all, since these frameworks are solely accessible for macOS plus you will have Xcode put in in your system, since some stuff in Swift the toolchain continues to be tied to the IDE, however why? 😢

Anyway, again to the subject, this is the boilerplate code for a macOS utility Swift script that may be began from the Terminal with one easy ./important.swift command and nothing extra.

#!/usr/bin/env swift

import AppKit
import SwiftUI

@accessible(macOS 10.15, *)
struct HelloView: View {
    var physique: some View {
        Textual content("Good day world!")
    }
}

@accessible(macOS 10.15, *)
class WindowDelegate: NSObject, NSWindowDelegate {

    func windowWillClose(_ notification: Notification) {
        NSApplication.shared.terminate(0)
    }
}


@accessible(macOS 10.15, *)
class AppDelegate: NSObject, NSApplicationDelegate {
    let window = NSWindow()
    let windowDelegate = WindowDelegate()

    func applicationDidFinishLaunching(_ notification: Notification) {
        let appMenu = NSMenuItem()
        appMenu.submenu = NSMenu()
        appMenu.submenu?.addItem(NSMenuItem(title: "Stop", motion: #selector(NSApplication.terminate(_:)), keyEquivalent: "q"))
        let mainMenu = NSMenu(title: "My Swift Script")
        mainMenu.addItem(appMenu)
        NSApplication.shared.mainMenu = mainMenu
        
        let dimension = CGSize(width: 480, peak: 270)
        window.setContentSize(dimension)
        window.styleMask = [.closable, .miniaturizable, .resizable, .titled]
        window.delegate = windowDelegate
        window.title = "My Swift Script"

        let view = NSHostingView(rootView: HelloView())
        view.body = CGRect(origin: .zero, dimension: dimension)
        view.autoresizingMask = [.height, .width]
        window.contentView!.addSubview(view)
        window.heart()
        window.makeKeyAndOrderFront(window)
        
        NSApp.setActivationPolicy(.common)
        NSApp.activate(ignoringOtherApps: true)
    }
}

let app = NSApplication.shared
let delegate = AppDelegate()
app.delegate = delegate
app.run()

Particular thanks goes to karwa for the authentic gist. Additionally in case you are into Storyboard-less macOS app improvement, it is best to undoubtedly check out this text by @kicsipixel. These assets helped me loads to place collectively what I wanted. I nonetheless needed to lengthen the gist with a correct menu setup and the activation coverage, however now this model acts like a real-world macOS utility that works like a attraction. There is just one challenge right here… the script file is getting crowded. 🙈

Swift Bundle Supervisor and macOS apps

So, if we comply with the identical logic, which means we are able to construct an executable bundle that may invoke AppKit associated stuff utilizing the Swift Bundle Supervisor. Simple as a pie. 🥧

mkdir MyApp
cd MyApp 
swift bundle init --type=executable

Now we are able to separate the elements into standalone recordsdata, we are able to additionally take away the supply checking, since we’ll add a platform constraint utilizing our Bundle.swift manifest file. If you do not know a lot about how the Swift Bundle Supervisor works, please learn my SPM tutorial, or in case you are merely curious in regards to the construction of a Bundle.swift file, you may learn my article in regards to the Swift Bundle manifest file. Let’s begin with the manifest updates.

import PackageDescription

let bundle = Bundle(
    title: "MyApp",
    platforms: [
        .macOS(.v10_15)
    ],
    dependencies: [
        
    ],
    targets: [
        .target(name: "MyApp", dependencies: []),
        .testTarget(title: "MyAppTests", dependencies: ["MyApp"]),
    ]
)

Now we are able to place the HelloView struct into a brand new HelloView.swift file.

import SwiftUI

struct HelloView: View {
    var physique: some View {
        Textual content("Good day world!")
    }
}

The window delegate can have its personal place inside a WindowDelegate.swift file.

import AppKit

class WindowDelegate: NSObject, NSWindowDelegate {

    func windowWillClose(_ notification: Notification) {
        NSApplication.shared.terminate(0)
    }
}

We are able to apply the identical factor to the AppDelegate class.

import AppKit
import SwiftUI

class AppDelegate: NSObject, NSApplicationDelegate {
    let window = NSWindow()
    let windowDelegate = WindowDelegate()

    func applicationDidFinishLaunching(_ notification: Notification) {
        let appMenu = NSMenuItem()
        appMenu.submenu = NSMenu()
        appMenu.submenu?.addItem(NSMenuItem(title: "Stop", motion: #selector(NSApplication.terminate(_:)), keyEquivalent: "q"))
        let mainMenu = NSMenu(title: "My Swift Script")
        mainMenu.addItem(appMenu)
        NSApplication.shared.mainMenu = mainMenu
        
        let dimension = CGSize(width: 480, peak: 270)
        window.setContentSize(dimension)
        window.styleMask = [.closable, .miniaturizable, .resizable, .titled]
        window.delegate = windowDelegate
        window.title = "My Swift Script"

        let view = NSHostingView(rootView: HelloView())
        view.body = CGRect(origin: .zero, dimension: dimension)
        view.autoresizingMask = [.height, .width]
        window.contentView!.addSubview(view)
        window.heart()
        window.makeKeyAndOrderFront(window)
        
        NSApp.setActivationPolicy(.common)
        NSApp.activate(ignoringOtherApps: true)
    }
}

Lastly we are able to replace the principle.swift file and provoke every little thing that must be finished.

import AppKit

let app = NSApplication.shared
let delegate = AppDelegate()
app.delegate = delegate
app.run()

The excellent news is that this strategy works, so you may develop, construct and run apps domestically, however sadly you may’t submit them to the Mac App Retailer, for the reason that ultimate utility bundle will not appear like an actual macOS bundle. The binary shouldn’t be code signed, plus you will want an actual macOS goal in Xcode to submit the applying. Then why hassle with this strategy?

Properly, simply because it’s enjoyable and I may even keep away from utilizing Xcode with the assistance of SourceKit-LSP and a few Editor configuration. The most effective half is that SourceKit-LSP is now a part of Xcode, so you do not have to put in something particular, simply configure your favourite IDE and begin coding.

You may as well bundle assets, since this function is offered from Swift 5.3, and use them by the Bundle.module variable if wanted. I already tried this, works fairly nicely, and it’s so a lot enjoyable to develop apps for the mac with out the additional overhead that Xcode comes with. 🥳