🔮Mirror

Reflection in Swift allows us to use the Mirror API to inspect and manipulate arbitrary values at runtime. 👉 SwiftLee

⬇️ 應用

💾 程式：paiza.io

• HasMirrors - use Mirror to inspect types.

• CaseReflectable - inspect enum case.

• NonNominalTypeWrapper - help inspect non-nominal types.

• enum case pattern - use Mirror to pattern match an enum case.

🔸 定義

// --------------------
//     Type aliases
// --------------------

// An element of the reflected instance’s structure
// label: nil | stored property name | enum case name.
typealias Mirror.Child = (label: String?, value: Any)

// The type used to represent substructure.
typealias Mirror.Children = AnyCollection<Mirror.Child>

// -------------
//     Types
// -------------

// Playgrounds and debugger will use this as suggestion to show subject.
enum Mirror.DisplayStyle {
    case `class`
    case collection
    case dictionary
    case `enum`
    case optional
    case set
    case `struct`
    case tuple
}

📗 參考

• SwiftLee ⟩ Reflection in Swift: How Mirror works
• AppVenture.me ⟩ The Swift Reflection API and what you can do with it
• Sundell ⟩ Reflection in Swift
• NSHipster ⟩ Mirror / Custom​Reflectable / Custom​Leaf​Reflectable

📘 手冊

• Swift ⟩

  • Debugging and Reflection ⟩ Mirror (struct)

    • Mirror.Child
    • Mirror.Children
    • Mirror.DisplayStyle
  • String ⟩

    • .init(reflecting:) - String(reflecting: subject) CustomDebugStringConvertible → CustomStringConvertible → TextOutputStreamable → Swift standard library
    • .init(describing:) - String(describing: subject) TextOutputStreamable → CustomStringConvertible → CustomDebugStringConvertible → Swift standard library
• Swift.org ⟩ How Mirror Works - how Mirror works under the hood.

👥 相關

• Pattern Matching ⟩ if/guard case let

• filter cases - use Mirror to do pattern matching.
• HasMirrors - helper protocol to mirror subjects.

• CaseReflectable - use Mirror to get enum case name/associated values.
• NonNominalTypeWrapper - wrap non-nominal types to conform to Loggable.

關鍵字：meta programming, reflection