Swift Optionals

How it works

An optional wraps either a present value or nil. Optional binding with if let gives a non-optional value inside the success branch. Nil is not the same thing as an empty string or zero. Give each outcome a meaning before selecting a fallback.

Run this Swift example

Install the toolchain for your platform from Swift.org, then check swift --version. The reviewed portable baseline is Swift 6.4.2 in Swift 6 mode on Ubuntu 26.04 x86_64 through the PC’s existing WSL installation. These are real Linux executions, not claims of Windows-native or Apple-platform test results. Windows Swift has separate C++/SDK prerequisites in its official setup guide.

Save the complete source as optionals.swift in a new learning folder. On Linux/macOS compile with swiftc -swift-version 6 -parse-as-library optionals.swift -o lesson, then run ./lesson. On a configured Windows toolchain use an output such as lesson.exe and run .\lesson.exe. The parse-as-library option supports the explicit @main entry point used by these sources. Compile each ordinary lesson separately.

Bhylu has no Swift browser runner. The JavaScript/Python editors do not run these sources; Apache, PHP and MySQL are not required. Downloads are source text, never executable teaching endpoints.

Download the complete optionals.swift · Download all source files with hash checks

For the optional collection, save download-examples.mjs in a new folder and run node download-examples.mjs. A local preview uses node download-examples.mjs http://127.0.0.1:8000/examples/swift/. It refuses an existing bhylu-swift-examples folder and installs or executes no Swift automatically. Apple-only files remain separate Xcode learning examples, not a portable Swift package target.

Example

@main
struct Lesson {
    static func main() {
        let note: String? = nil
        if let note {
            print(note)
        } else {
            print("No collection note")
        }
        let count: Int? = 0
        print(count ?? 99)
    }
}

Expected result

No collection note
0

The missing note has its own branch. The present integer zero remains zero because the fallback is used only for nil. Avoid inventing a normal-looking value when absence should stop an operation.