Swift Mirror

Swift 通过 Mirror 在运行时检测、访问或者修改类型的行为的特性。

struct Person {
  let name: String
  let age: Int
}

let xiaoMing = Person(name: "XiaoMing", age: 16)
let r = Mirror(reflecting: xiaoMing)

print("属性个数:\(r.children.count)")
// 通过 Mirror 初始化得到的结果中包含的元素的描述都被集合在 children 属性下
// 其类型是 `public typealias Children = AnyCollection<Mirror.Child>`
for i in r.children {
  print("属性名:\(i)")
}
/*
 属性名:(Optional("name"), "XiaoMing")
 属性名:(Optional("age"), 16)
 */

// 也可以通过 `dump` 快速输出某个对象
dump(xiaoMing)
/*
 ▿ Person
 - name: "XiaoMing"
 - age: 16
 */

也可以使用 Mirror 来达到 Objecttive-C 中 KVC 的效果：

func valueFrom(object: Any, key: String) -> Any? {
  let mirror = Mirror(reflecting: object)

  for i in mirror.children {
    let (targetKey, targetMirror) = i
    if key == targetKey {
      return targetMirror
    }
  }

  return nil
}

if let name = valueFrom(object: xiaoMing, key: "name") as? String {
  print("通过 key 得到值: \(name)")
}

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参考

Swift Mirror