# Swift — Apple Modern Programming Language

> Swift is a powerful and intuitive programming language for building apps for iOS, macOS, watchOS, tvOS, Linux, and the server. Created at Apple to replace Objective-C. Fast, safe, and expressive with protocol-oriented design.

## Install

Save in your project root:

## Quick Use

```bash
# macOS: comes with Xcode
xcode-select --install

# Linux
# Download from https://www.swift.org/download

# Or via swiftly version manager
curl -L https://swift-server.github.io/swiftly/swiftly-install.sh | bash
swiftly install latest

swift --version
```

Hello world:
```swift
// main.swift
import Foundation

let users = [
    (name: "Alice", score: 95),
    (name: "Bob",   score: 87),
    (name: "Carol", score: 91),
]

let sorted = users.sorted { $0.score > $1.score }
for user in sorted {
    print("\(user.name): \(user.score)")
}
```

Swift Package Manager:
```bash
mkdir MyCLI && cd MyCLI
swift package init --type executable
swift build
swift run
swift test
swift package update
```

## Intro

Swift is a powerful and intuitive programming language developed by Apple, first announced at WWDC 2014. Designed to replace Objective-C while remaining interoperable with it. Swift is fast (compiled to native code via LLVM), safe (eliminates entire classes of bugs with optionals, value types, and memory-safety features), and expressive (modern syntax, closures, generics, protocol-oriented programming).

- **Repo**: https://github.com/swiftlang/swift (formerly apple/swift)
- **Stars**: 69K+
- **License**: Apache 2.0

## What Swift Does

- **Native compilation** — LLVM-based, native ARM/x86/WASM
- **Optionals** — no nil pointer crashes
- **Value types** — structs, enums with associated values
- **Protocols** — structural polymorphism, protocol extensions
- **Generics** — parameterized types and functions
- **Closures** — first-class, trailing syntax
- **Concurrency** — async/await + actors (Swift 5.5+)
- **SwiftUI** — declarative UI framework
- **Swift Package Manager** — built-in dep/build tool
- **Interop** — Objective-C, C, and C++ interop
- **Cross-platform** — macOS, iOS, watchOS, tvOS, Linux, Windows

## Architecture

Swift compiler built on LLVM. Uses Automatic Reference Counting (ARC) for memory management — no GC pauses. Modules and package format replace Objective-C frameworks. SwiftUI uses result builders and property wrappers for declarative UI.

## Self-Hosting

Language toolchain.

## Key Features

- Protocol-oriented programming
- Value types and copy-on-write
- Async/await and actors
- Swift Concurrency (structured concurrency)
- Result builders for DSLs
- Property wrappers
- Swift Package Manager
- Server-side frameworks (Vapor, Hummingbird)
- Interop with Objective-C and C++
- Linux and Windows support

## Comparison

| Language | Memory | Concurrency | Interop |
|---|---|---|---|
| Swift | ARC | async + actors | ObjC, C, C++ |
| Rust | Ownership | async | C, C++ |
| Kotlin | GC (JVM) | Coroutines | Java |
| C# | GC | async/await | .NET |
| Go | GC | Goroutines | C (cgo) |

## 常见问题 FAQ

**Q: 只能 Apple 平台？**
A: 不。Swift 是跨平台开源语言，官方支持 macOS、iOS、Linux、Windows。Vapor、Hummingbird 等 server framework 用于后端。

**Q: 和 Objective-C 关系？**
A: Swift 完全兼容 ObjC（互调、共享项目）。Apple 新 API 优先 Swift。老项目可以渐进迁移。

**Q: Swift Concurrency 能取代 GCD 吗？**
A: 大部分场景可以。async/await + actor 解决数据竞争。GCD 仍然是底层工具，但高层代码推荐 Swift Concurrency。

## 来源与致谢 Sources

- Docs: https://www.swift.org/documentation
- GitHub: https://github.com/swiftlang/swift
- License: Apache 2.0

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Source: https://tokrepo.com/en/workflows/7cce7840-3606-11f1-9bc6-00163e2b0d79
Author: AI Open Source