[英]Can Swift convert a class / struct data into dictionary?
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 將包含以下內容:
{"name": "Alex", "age": 30, height: 170}
這在 Swift 中可能嗎?
我可以訪問像字典這樣的類嗎,例如可能使用:
test.value(forKey: "name");
或類似的東西?
您只需將一個計算屬性添加到您的struct
中,即可返回帶有您的值的Dictionary
。 請注意,Swift 本機字典類型沒有任何稱為value(forKey:)
的方法。 您需要將Dictionary
轉換為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
}
}
您還可以按照@ColGraff 發布的鏈接答案中的建議擴展Encodable
協議,以使其對所有Encodable
結構具有通用性:
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
您可以像這樣使用 Reflection 和 Mirror 來使其更具動態性並確保您不會忘記某個屬性。
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)
[“名稱”:“瑞恩”,“位置”:2,“好”:真,“汽車”:“福特”]
聚會有點晚了,但我認為這是JSONEncoder
和JSONSerialization
的絕佳機會。 接受的答案確實涉及到這一點,這個解決方案可以節省我們每次訪問密鑰時調用JSONSerialization
的時間,但同樣的想法!
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)
}
}
然后,如果Encodable
應表示為 JSON 中的對象(例如 Swift Array
將是 JSON 數組),則可以使用JSONSerialization
創建Dictionary
這是一個例子:
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)
輸出:
{
"numberOfDoors" : 5,
"datePurchased" : "2020-03-04T16:04:13Z",
"name" : "Mazda 2",
"cost" : 1234.5599999999999,
"isCompanyCar" : true
}
使用協議,這是一個優雅的解決方案。
1. 將結構或類編碼為數據
2. 解碼數據並傳輸到字典。
/// 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")
參考: 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/
這個答案就像上面使用 Mirror 的答案。 但是考慮嵌套類/結構的情況。
extension Encodable {
func dictionary() -> [String:Any] {
var dict = [String:Any]()
let mirror = Mirror(reflecting: self)
for child in mirror.children {
guard let key = child.label else { continue }
let childMirror = Mirror(reflecting: child.value)
switch childMirror.displayStyle {
case .struct, .class:
let childDict = (child.value as! Encodable).dictionary()
dict[key] = childDict
case .collection:
let childArray = (child.value as! [Encodable]).map({ $0.dictionary() })
dict[key] = childArray
case .set:
let childArray = (child.value as! Set<AnyHashable>).map({ ($0 as! Encodable).dictionary() })
dict[key] = childArray
default:
dict[key] = child.value
}
}
return dict
}
}
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