Editing Entry point (section)

===Swift===
When run in an [[Xcode]] Playground,<ref>Not to be confused with [https://www.apple.com/swift/playgrounds/ Swift Playgrounds] {{Webarchive|url=https://web.archive.org/web/20220708182700/https://www.apple.com/swift/playgrounds/ |date=2022-07-08 }}, an Apple-developed iPad app for learning the Swift programming language.</ref> [[Swift (programming language)|Swift]] behaves like a scripting language, executing statements from top to bottom; top-level code is allowed.

<syntaxhighlight lang="swift">
// HelloWorld.playground

let hello = "hello"
let world = "world"

let helloWorld = hello + " " + world

print(helloWorld) // hello world
</syntaxhighlight>

[[Cocoa (API)|Cocoa]]- and [[Cocoa Touch]]-based applications written in Swift are usually initialized with the <code>@NSApplicationMain</code> and <code>@UIApplicationMain</code> attributes, respectively. Those attributes are equivalent in their purpose to the <code>main.m</code> file in [[Objective-C]] projects: they implicitly declare the <code>main</code> function that calls <code>UIApplicationMain(_:_:_:_:)</code><ref>{{Cite web|url=https://developer.apple.com/documentation/uikit/1622933-uiapplicationmain|title=UIApplicationMain(_:_:_:_:) — UIKit|website=Apple Developer Documentation|access-date=2019-01-12|archive-date=2019-01-12|archive-url=https://web.archive.org/web/20190112195043/https://developer.apple.com/documentation/uikit/1622933-uiapplicationmain|url-status=live}}</ref> which creates an instance of <code>UIApplication</code>.<ref>{{Cite web|url=https://developer.apple.com/documentation/uikit/uiapplication|title=UIApplication — UIKit|website=Apple Developer Documentation|access-date=2019-01-12|archive-date=2019-01-13|archive-url=https://web.archive.org/web/20190113062642/https://developer.apple.com/documentation/uikit/uiapplication|url-status=live}}</ref>

The following code is the default way to initialize a Cocoa Touch-based [[iOS]] app and declare its application delegate.<syntaxhighlight lang="swift">
// AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    
    var window: UIWindow?
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        return true
    }
    
}
</syntaxhighlight>