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Swift Conversions and Type Casting

Distinguish a failed text conversion from a runtime type mismatch.

How it works

Int(text) is a failable conversion and returns an optional. as? conditionally casts a value whose dynamic type may match a requested type. Converting representation and checking dynamic type are separate tasks. A successful integer conversion still needs business-domain validation.

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 conversions-casting.swift in a new learning folder. On Linux/macOS compile with swiftc -swift-version 6 -parse-as-library conversions-casting.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 conversions-casting.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

conversions-casting.swift


@main
struct Lesson {
    static func main() {
        print(Int("24") ?? -1)
        print(Int("two") == nil)
        let value: Any = "Cedar"
        print(value as? String ?? "Unknown")
    }
}

Expected result

24
true
Cedar

The fallback -1 is only a visible demonstration of an absent result; it is not a recommended stored duration. The conditional cast yields a String only when the actual value supports it.

Primary references: The Swift Programming Language and Apple framework documentation. Use the selected platform’s current requirements. Fictional workshop examples do not establish production safety or deployment approval.

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