🤖Compiler Directives

📗 參考

• Using compiler directives in Swift - Sundell

• Feature flags in Swift - Sundell

• Compiler Directives - Elements Docs

• Understanding @inlinable in Swift - SwiftRocks

👥 相關

• Swift ⟩ Attributes

• Debugging

🗣 討論

• Macros in Swift? - custom log function using #file, #line, #function ⭐️

Compilation Condition: #if

• #if DEBUG

• #if <compilation flag> 👉 Feature flags in Swift

• #if targetEnvironment( )

#if DEBUG

func log(_ expression: @autoclosure () -> Any) {
    // print a given expression only within debug builds
    #if DEBUG
    print(expression())
    #endif
}

#if os( )

struct EditorView: View {
    //...
    var body: some View {
    
        #if os(tvOS)
        CanvasView()
        #else
        CanvasView().gesture(DragGesture().onChanged { state in
          // ...
        })
        #endif
        // ...
    }
}

#if targetEnvironment( )

func setupTabBarController(_ controller: UITabBarController) {
    var viewControllers = [UIViewController]()

    #if targetEnvironment(simulator)
    viewControllers.append(DebugViewController())
    #endif

    controller.viewControllers = viewControllers
}