ObjectMapper如何基于JSON映射不同的对象
我正在使用ObjectMapper（https://github.com/Hearst-
DD/ObjectMapper）将JSON映射到Swift对象。
说我有这个JSON结构：
{ animals: [
{
"type": "Cat",
"weight": 23,
"catchMice": true
},
{
"type": "Fish",
"weight": 1,
"swim": true
}
]
}
我有以下Swift对象：
class Foo: Mappable { var animals: [Animal] = []
func mapping(map: Map) {
animals <- map["animals"] //But I want to be able to distinguish between Cat and Fish objects here
}
}
class Animal: Mappable {
var type: String?
var weight: Double?
required init?(map: Map) {}
func mapping(map: Map) {
type <- map["type"]
weight <- map["weight"]
}
}
class Cat: Animal { // How do I make use of this class
var catchMice: Bool?
}
class Fish: Animal { // How do I make use of this class
var swim: Bool?
}
如何使用JSON对象中的键区分映射Cat和Fish映射type？非常感谢！
回答：
回答：
- Xcode 10.2.1（10E1001），Swift 5
回答：
{ "animals": [
{
"id": 1,
"name": "Cat",
"type": "cat",
"weight": 23,
"area": ["home", "street"],
"can_climb_trees": true,
"competence": [
{ "id": 1, "name": "to catch mouse" },
{ "id": 2, "name": "to mew" },
{ "id": 3, "name": "to wake people up in the morning" },
{ "id": 4, "name": "to eat fish" }
]
},
{
"id": 2,
"name": "fish",
"type": "fish",
"weight": 1,
"area": ["ocean", "lake"],
"can_swim": false,
"competence": [
{ "id": 5, "name": "to swim" },
{ "id": 6, "name": "to tease a cat" }
]
},
{
"id": 3,
"name": "dog",
"weight": 55,
"area": ["house", "street"],
"competence": [
{ "id": 5, "name": "to bring newspaper" },
{ "id": 6, "name": "to a good booy" }
]
},
{
"id": 4,
"name": "Cat",
"type": "cat",
"weight": 23,
"area": ["home", "street"],
"can_climb_trees": true,
"competence": [
{ "id": 1, "name": "to catch mouse" },
{ "id": 2, "name": "to mew" },
{ "id": 3, "name": "to wake people up in the morning" },
{ "id": 4, "name": "to eat fish" }
]
}
]
}
回答：
检测数组中的对象
import Foundationimport ObjectMapper
class AnimalsArrayTransformType: TransformType {
public typealias Object = [Animal]
public typealias JSON = [[String: Any]]
func transformToJSON(_ value: [Animal]?) -> [[String : Any]]? {
guard let animals = value else { return nil }
return animals.map { $0.toJSON() }
}
func transformFromJSON(_ value: Any?) -> [Animal]? {
guard let animals = value as? [[String: Any]] else { return nil }
return animals.compactMap { dictionary -> Animal? in
if let cat = Cat(JSON: dictionary) { return cat }
if let fish = Fish(JSON: dictionary) { return fish }
if let animal = Animal(JSON: dictionary) { return animal }
return nil
}
}
}
映射类
import Foundationimport ObjectMapper
class Animals: Mappable, CustomStringConvertible {
private(set) var animals: [Animal] = []
required init?(map: Map) { }
func mapping(map: Map) {
animals <- (map["animals"], AnimalsArrayTransformType())
}
}
class BaseObject: Mappable, CustomStringConvertible {
private(set) var id: Int?
private(set) var name: String?
required init?(map: Map) { mapping(map: map) }
func mapping(map: Map) {
id <- map["id"]
name <- map["name"]
}
}
class Animal: BaseObject {
private(set) var type: String?
private(set) var weight: Double?
private(set) var area: [String]?
private(set) var competence: [BaseObject]?
required init?(map: Map) { super.init(map: map) }
override func mapping(map: Map) {
super.mapping(map: map)
type <- map["type"]
weight <- map["weight"]
area <- map["area"]
competence <- map["competence"]
}
}
class Cat: Animal {
private(set) var canClimbTrees: Bool?
required init?(map: Map) {
super.init(map: map)
if canClimbTrees == nil { return nil }
}
override func mapping(map: Map) {
super.mapping(map: map)
canClimbTrees <- map["can_climb_trees"]
}
}
class Fish: Animal {
private(set) var canSwim: Bool?
required init?(map: Map) {
super.init(map: map)
if canSwim == nil { return nil }
}
override func mapping(map: Map) {
super.mapping(map: map)
canSwim <- map["can_swim"]
}
}
帮手
extension Mappable { var description: String {
return toJSONString(prettyPrint: true) ?? "\(self)"
}
}
用法（从文件读取json）
func sample() { if let path = Bundle.main.path(forResource: "data", ofType: "json") {
do {
let text = try String(contentsOfFile: path, encoding: .utf8)
if let dict = try JSONSerialization.jsonObject(with: text.data(using: .utf8)!, options: JSONSerialization.ReadingOptions.allowFragments) as? [String: Any] {
if let data = Animals(JSON: dict) {
print(data.animals.map {"class: \(type(of: $0))" }.joined(separator: ", ") )
// class: Cat, class: Fish, class: Animal
print("===============\n\(data)")
}
}
}catch {
print("\(error.localizedDescription)")
}
}
}
回答：
检测数组中的对象
class Animals: Codable { fileprivate enum CodingKeys: String, CodingKey {
case animals
}
private(set) var animals: [Animal]
required init(from decoder: Decoder) throws {
self.animals = []
let container = try decoder.container(keyedBy: CodingKeys.self)
var unkeyedDecodingContainer = try container.nestedUnkeyedContainer(forKey: .animals)
while !unkeyedDecodingContainer.isAtEnd {
if let obj = try? unkeyedDecodingContainer.decode(Cat.self) {
animals.append(obj)
continue
}
if let obj = try? unkeyedDecodingContainer.decode(Fish.self) {
animals.append(obj)
continue
}
if let obj = try? unkeyedDecodingContainer.decode(Animal.self) {
animals.append(obj)
continue
}
}
}
}
映射类
enum AnimalType: String, Codable { case cat = "cat", fish = "fish"
}
class BaseObject: Codable {
private(set) var id: Int?
private(set) var name: String?
}
class Animal: BaseObject {
private(set) var type: AnimalType?
private(set) var weight: Int?
private(set) var area: [String]?
private(set) var competence: [BaseObject]?
private enum CodingKeys: String, CodingKey {
case type, weight, area, competence
}
override func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encodeIfPresent(type, forKey: .type)
try container.encodeIfPresent(weight, forKey: .weight)
try container.encodeIfPresent(area, forKey: .area)
try container.encodeIfPresent(competence, forKey: .competence)
try super.encode(to: encoder)
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
type = try container.decodeIfPresent(AnimalType.self, forKey: .type)
weight = try container.decodeIfPresent(Int.self, forKey: .weight)
area = try container.decodeIfPresent([String].self, forKey: .area)
competence = try container.decodeIfPresent([BaseObject].self, forKey: .competence)
try super.init(from: decoder)
}
}
class Cat: Animal {
private(set) var canClimbTrees: Bool
private enum CodingKeys: String, CodingKey {
case canClimbTrees = "can_climb_trees"
}
override func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encodeIfPresent(canClimbTrees, forKey: .canClimbTrees)
try super.encode(to: encoder)
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.canClimbTrees = try container.decode(Bool.self, forKey: .canClimbTrees)
try super.init(from: decoder)
}
}
class Fish: Animal {
private(set) var canSwim: Bool
enum CodingKeys: String, CaseIterable, CodingKey {
case canSwim = "can_swim"
}
override func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encodeIfPresent(canSwim, forKey: .canSwim)
try super.encode(to: encoder)
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.canSwim = try container.decode(Bool.self, forKey: .canSwim)
try super.init(from: decoder)
}
}
帮手
extension Decodable where Self : Encodable { dynamic func format(options: JSONEncoder.OutputFormatting) -> String {
let encoder = JSONEncoder()
encoder.outputFormatting = options
do {
let jsonData = try encoder.encode(self)
if let jsonString = String(data: jsonData, encoding: .utf8) { return "\(jsonString)" }
} catch {
print("\(error.localizedDescription)")
}
return "nil"
}
}
用法（从文件读取json）
func sample() { if let path = Bundle.main.path(forResource: "data", ofType: "json") {
do {
guard let data = try String(contentsOfFile: path, encoding: .utf8).data(using: .utf8) else { return }
let decoder = JSONDecoder()
let result = try decoder.decode(Animals.self, from: data)
print(result.animals.map {"\(type(of: $0))" } )
//print("===============")
//print(result.format(options: .prettyPrinted))
} catch let error {
print("\(error.localizedDescription)")
}
}
}
回答：
[“猫”，“鱼”，“动物”，“猫”]
以上是 ObjectMapper如何基于JSON映射不同的对象 的全部内容， 来源链接： utcz.com/qa/399046.html
