Guard Let

While if let unwraps an optional and runs code when a value exists, guard let takes the opposite approach — it exits early when a value is missing. This is especially useful inside functions where you want to handle the "bad" case first and keep the main logic clean.

func greet(name: String?) {
    guard let unwrappedName = name else {
        print("No name provided")
        return
    }
    print("Hello, \(unwrappedName)!")
}

greet(name: "Taylor") // Hello, Taylor!
greet(name: nil)      // No name provided

The guard let statement checks if name has a value. If it doesn't, the else block runs and the function exits with return. If the optional contains a value, it's unwrapped into unwrappedName — and here's the key difference from if let: the unwrapped variable remains available for the rest of the function, not just inside a block.

This "early exit" pattern keeps your code readable by handling error cases upfront, so the main logic isn't nested inside multiple if statements.