Hello World in Swift

Every programming journey starts with Hello World. Let’s write our first Swift program.

The Code

Create a file named hello.swift:

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print("Hello, World!")

That’s it! Swift’s clean syntax means Hello World is just a single line.

Understanding the Code

• print() - A global function that outputs text to the console
• "Hello, World!" - A String literal enclosed in double quotes
• No semicolon - Swift doesn’t require semicolons at the end of statements
• No main function - Top-level code runs automatically in Swift scripts

Running with Docker

The easiest way to run this without installing Swift locally:

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# Pull the official Swift image
docker pull swift:6.0

# Run the program
docker run --rm -v $(pwd):/app -w /app swift:6.0 swift hello.swift

Running Locally

If you have Swift installed (comes with Xcode on macOS):

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# Run directly as a script
swift hello.swift

# Or compile and run
swiftc hello.swift -o hello
./hello

Expected Output

Hello, World!

Key Concepts

1. Swift is concise - No boilerplate required for simple programs
2. Scripts vs Applications - .swift files can run directly or be compiled
3. Type inference - Swift figures out types automatically
4. Modern syntax - Clean, readable code without unnecessary ceremony

A More Detailed Version

For a slightly more structured approach:

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import Foundation

// A proper greeting function
func greet(name: String) -> String {
    return "Hello, \(name)!"
}

// Call the function
let message = greet(name: "World")
print(message)

This version demonstrates:

• import Foundation - Swift’s core library (not needed for basic print)
• Function definition - Using func with named parameters
• String interpolation - Embedding values with \()
• Constants - Using let for immutable values
• Type annotations - Explicit String types (optional due to inference)

Why Swift Stands Out

Coming from other languages, you’ll notice Swift’s unique characteristics:

• No header files - Everything in one .swift file
• Named parameters - greet(name: "World") is self-documenting
• Optionals - Built-in null safety (we’ll cover this later)
• Protocol-oriented - Composition over inheritance

Next Steps

Continue to Variables and Data Types to learn about Swift’s powerful type system, including optionals, value types, and type inference.