Swift 可以将类/结构数据转换为字典吗？

Question

例如：

class Test {
    var name: String;
    var age: Int;
    var height: Double;
    func convertToDict() -> [String: AnyObject] { ..... }
}

let test = Test();
test.name = "Alex";
test.age = 30;
test.height = 170;

let dict = test.convertToDict();

dict 会有内容：

{"name": "Alex", "age": 30, height: 170}

这在 Swift 中可行吗？

我可以访问像字典这样的类吗，例如可能使用：

test.value(forKey: "name");

或者类似的？

谢谢。

Answer 1

您只需将计算属性添加到您的 struct 即可返回带有您的值的 Dictionary。请注意，Swift 本机字典类型没有任何称为 value(forKey:) 的方法。您需要将您的 Dictionary 转换为 NSDictionary：

struct Test {
    let name: String
    let age: Int
    let height: Double
    var dictionary: [String: Any] {
        return ["name": name,
                "age": age,
                "height": height]
    }
    var nsDictionary: NSDictionary {
        return dictionary as NSDictionary
    }
}

---

您还可以按照@ColGraff 发布的链接答案中的建议扩展Encodable 协议，使其适用于所有Encodable 结构：

struct JSON {
    static let encoder = JSONEncoder()
}
extension Encodable {
    subscript(key: String) -> Any? {
        return dictionary[key]
    }
    var dictionary: [String: Any] {
        return (try? JSONSerialization.jsonObject(with: JSON.encoder.encode(self))) as? [String: Any] ?? [:]
    }
}

---

struct Test: Codable {
    let name: String
    let age: Int
    let height: Double
}

let test = Test(name: "Alex", age: 30, height: 170)
test["name"]    // Alex
test["age"]     // 30
test["height"]  // 170

Answer 2

您可以像这样使用 Reflection 和 Mirror 来使其更具动态性并确保您不会忘记某个属性。

struct Person {
  var name:String
  var position:Int
  var good : Bool
  var car : String

  var asDictionary : [String:Any] {
    let mirror = Mirror(reflecting: self)
    let dict = Dictionary(uniqueKeysWithValues: mirror.children.lazy.map({ (label:String?, value:Any) -> (String, Any)? in
      guard let label = label else { return nil }
      return (label, value)
    }).compactMap { $0 })
    return dict
  }
}


let p1 = Person(name: "Ryan", position: 2, good : true, car:"Ford")
print(p1.asDictionary)

["name": "Ryan", "position": 2, "good": true, "car": "Ford"]

Answer 3

使用协议，这是一个优雅的解决方案。
1. 将结构或类编码为数据
2。解码数据并传输到字典。

/// define protocol convert Struct or Class to Dictionary
protocol Convertable: Codable {

}

extension Convertable {

    /// implement convert Struct or Class to Dictionary
    func convertToDict() -> Dictionary<String, Any>? {

        var dict: Dictionary<String, Any>? = nil

        do {
            print("init student")
            let encoder = JSONEncoder()

            let data = try encoder.encode(self)
            print("struct convert to data")

            dict = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? Dictionary<String, Any>

        } catch {
            print(error)
        }

        return dict
    }
}

struct Student: Convertable {

    var name: String
    var age: Int
    var classRoom: String

    init(_ name: String, age: Int, classRoom: String) {
        self.name = name
        self.age = age
        self.classRoom = classRoom
    }
}

let student = Student("zgpeace", age: 18, classRoom: "class one")

print(student.convertToDict() ?? "nil")

参考：https://a1049145827.github.io/2018/03/02/Swift-%E4%BB%8E%E9%9B%B6%E5%AE%9E%E7%8E%B0%E4%B8%80%E4%B8%AAStruct%E6%88%96Class%E8%BD%ACDictionary%E7%9A%84%E9%9C%80%E6%B1%82/

Answer 4

聚会有点晚了，但我认为这是JSONEncoder 和JSONSerialization 的绝佳机会。 接受的答案确实涉及到这一点，这个解决方案让我们每次访问密钥时都调用JSONSerialization，但同样的想法！

extension Encodable {

    /// Encode into JSON and return `Data`
    func jsonData() throws -> Data {
        let encoder = JSONEncoder()
        encoder.outputFormatting = .prettyPrinted
        encoder.dateEncodingStrategy = .iso8601
        return try encoder.encode(self)
    }
}

如果Encodable 应表示为 JSON 中的对象（例如 Swift Array 将是 JSON 数组），则您可以使用 JSONSerialization 创建 Dictionary

这是一个例子：

struct Car: Encodable {
    var name: String
    var numberOfDoors: Int
    var cost: Double
    var isCompanyCar: Bool
    var datePurchased: Date
    var ownerName: String? // Optional
}

let car = Car(
    name: "Mazda 2",
    numberOfDoors: 5,
    cost: 1234.56,
    isCompanyCar: true,
    datePurchased: Date(),
    ownerName: nil
)

let jsonData = try car.jsonData()

// To get dictionary from `Data`
let json = try JSONSerialization.jsonObject(with: jsonData, options: [])
guard let dictionary = json as? [String : Any] else {
    return
}

// Use dictionary

guard let jsonString = String(data: jsonData, encoding: .utf8) else {
    return
}

// Print jsonString
print(jsonString)

输出：

{
  "numberOfDoors" : 5,
  "datePurchased" : "2020-03-04T16:04:13Z",
  "name" : "Mazda 2",
  "cost" : 1234.5599999999999,
  "isCompanyCar" : true
}