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Your First App: Hello, World!

Time to build something real. In this lesson you'll create a new project, run it on a simulated iPhone, understand every line of the starter code, and make your first change. By the end you'll have a working app with your own message on screen.

Step by step

1. Create a new project

   Open Xcode. On the Welcome window choose Create New Project (or menu File → New → Project…).

2. Pick the App template

   Make sure the iOS tab is selected at the top, choose App, and click Next.

3. Configure your app

   Fill in the options:

   • Product Name: HelloWorld
   • Organization Identifier: com.yourname (any reverse-domain text)
   • Interface: SwiftUI
   • Language: Swift

   Click Next, choose a folder to save it in, then Create.

4. Meet the Xcode workspace

   Xcode opens your project. On the left is the Navigator (your files), in the middle the Editor (your code), and on the right the Canvas — a live preview of your app.

5. Choose a simulator

   At the top of the window, next to the Run button, click the device menu and pick an iPhone (e.g. iPhone 16 Pro). The Simulator is a virtual iPhone that runs on your Mac — no physical device needed.

6. Run your app

   Press the ▶ Run button (or ⌘ + R). Xcode builds the app and launches the Simulator. After a moment you'll see “Hello, world!” on a simulated iPhone screen. That's your first app running!

Understanding the starter code

Open ContentView.swift in the Navigator. SwiftUI generates something like this for a new project:

import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundStyle(.tint)
            Text("Hello, world!")
        }
        .padding()
    }
}

#Preview {
    ContentView()
}

ContentView.swift — the screen you saw running.

Let's break it down line by line:

• import SwiftUI — brings in Apple's UI framework so you can use its tools.
• struct ContentView: View — defines a screen. The : View part promises "this is something SwiftUI can display."
• var body: some View — the body describes what appears on screen. Whatever you put here is your UI.
• VStack { ... } — a Vertical Stack: it arranges the things inside it top-to-bottom.
• Image(systemName: "globe") — shows a built-in system icon (the small globe). .imageScale and .foregroundStyle are modifiers that style it.
• Text("Hello, world!") — displays the text label.
• .padding() — adds breathing room around the stack.
• #Preview { ... } — powers the live Canvas preview on the right, so you see changes without running the full app.

Make it yours

Let's change the message. Replace the Text line and add a few modifiers:

Text("Hello, iOS! 👋")
    .font(.largeTitle)
    .fontWeight(.bold)
    .foregroundStyle(.blue)

A bigger, bold, blue greeting.

The Canvas preview updates instantly. Press ⌘ + R again to see it in the Simulator. Congratulations — you just edited a live iOS app.

What just happened

You learned the core loop of iOS development:

1. Create a project from the App template.
2. Describe your UI in SwiftUI's body.
3. Preview changes live in the Canvas.
4. Run on the Simulator with ⌘ + R.

Every app you'll ever build — from a to-do list to a full social network — is this same loop, repeated and layered. You're officially an iOS developer now.