【KakaJSON手册】01_JSON转Model_01_基本用法

在iOS开发中，后台返回的数据大多是JSON格式，对应地会被网络框架层解析成Swift中的Dictionary、Array。由于数据类型的复杂、字段的繁多，直接使用Dictionary、Array会比较麻烦，比如items[0]["user"]["name"]这样的使用方式，非常不友善，而且没有智能语法提示。所以很多时候会考虑将JSON转换成Model之后再进行操作，会友善很多，比如items[0].user.name。

• Swift内置了一套Codable机制，可以用于JSON转Model。对于一些简单的模型结构，还是挺好用，但一旦牵扯到复杂的模型结构、一些个性化的需求（比如KeyMapping、类型不匹配时的转换处理、自定义解析规则等），Codable就不太能友善地完成任务了。
• 为了解决上述问题，我编写了一套纯Swift实现的JSON与Model互相转换的框架：KakaJSON，本人非常喜欢龙珠，框架取名自Kaka Rotto(卡卡罗特，孙悟空)
• KakaJSON通过了大量的单元测试用例（目前有80多个测试用例，未来会增加到上百个测试用例，也非常欢迎大家提供各种应用场景和测试用例），应对各种常用的数据场景，对外提供了一些友善易用、扩展性强、可高度个性化定制需求的接口，内置了Metedata缓存等机制，加快转换速度。
• 本教程是为了让大家能够快速上手KakaJSON，挖掘它内部的各种功能，发挥它的最大威力。未来也可能会推出一些源码分析的文章。
• 本文是《KakaJSON手册》系列文章的第一篇

---

最简单的Model

import KakaJSON

// ① 让模型类型遵守`Convertible`协议
struct Cat: Convertible {
    var name: String = ""
    var weight: Double = 0.0
}

// json也可以是NSDictionary、NSMutableDictionary类型
let json: [String: Any] = [
    "name": "Miaomiao",
    "weight": 6.66
]

// ② 直接调用json的model方法，传入模型类型，返回模型实例
let cat1 = json.kj.model(Cat.self)
XCTAssert(cat1.name == "Miaomiao")
XCTAssert(cat1.weight == 6.66)

// 或者也可以调用一个全局函数来完成JSON转模型
let cat2 = model(from: json, Cat.self)

Type Variable

// 有时类型可能是个变量，比如
var type: Convertible.Type = Cat.self

// 调用带有type参数的方法即可
// 由于传入的类型是Convertible.Type变量，因此返回值类型是Convertible，到时根据需求强制转换成自己想要的类型
let cat1 = json.kj.model(type: type) as? Cat

// 或者调用全局函数
let cat2 = model(from: json, type: type) as? Cat

Class类型

class Cat: Convertible {
    var weight: Double = 0.0
    var name: String = ""
    // 由于Swift初始化机制的原因，`Convertible`协议强制要求实现init初始化器
    // 这样框架内部才可以完整初始化一个实例
    required init() {}
}
let json = ...
let cat = json.kj.model(Cat.self)

// 继承自NSObject的类也是一样的用法
class Person: NSObject, Convertible {
    var name: String = ""
    var age: Int = 0
    // 由于NSObject内部已经有init，因此Person算是重载init，需再加上`override`
    required override init() {}
}
let person = json.kj.model(Person.self)

struct Dog: Convertible {
    var weight: Double = 0.0
    var name: String = ""
    // 由于编译器自动帮结构体类型生成了一个init初始化器
    // 所以不需要自己再实现init初始化器
}

struct Pig: Convertible {
    var weight: Double
    var name: String
    // 如果没有在定义属性的同时指定初始值，编译器是不会为结构体生成init初始化器的
    // 所以需要自己实现init初始化器
    init() {
        name = ""
        weight = 0.0
    }
}

继承

// 有继承的情况也是照常使用即可

class Person: Convertible {
    var name: String = ""
    var age: Int = 0
    required init() {}
}

class Student: Person {
    var score: Int = 0
    var no: String = ""
}

let json: [String: Any] = [
    "name": "jack",
    "age": 18,
    "score": 98,
    "no": "9527"
]

let student = json.kj.model(Student.self)

let属性

// KakaJSON也支持let属性

struct Cat: Convertible {
    // 测试表明：在真机release模式下，对数字类型的let限制比较严格
    // 值虽然修改成功了（可以打印Cat结构体发现weight已经改掉了），但get出来还是0.0
    // 所以建议使用`private(set) var`取代`let`
    private(set) var weight: Double = 0.0
    let name: String = ""
}
let json = ...
let cat = json.kj.model(Cat.self)

NSNull

struct Cat: Convertible {
    var weight: Double = 0.0
    var name: String = "xx"
    var data: NSNull?
}

let json: [String: Any] = [
    "name": NSNull(),
    "weight": 6.6,
    "data": NSNull()
]

let cat = json.kj.model(Cat.self)
// 转换失败，保留默认值
XCTAssert(cat.name == "xx")
XCTAssert(cat.weight == 6.6)
XCTAssert(cat.data == NSNull())

JSONString

// jsonString也可以是NSString、NSMutableString类型
let jsonString = """
{
    "name": "Miaomiao",
    "weight": 6.66
}
"""

// 跟JSON的用法是一样的
let cat1 = jsonString.kj.model(Cat.self)
let cat2 = model(from: jsonString, Cat.self)

var type: Convertible.Type = Cat.self
let cat3 = jsonString.kj.model(type: type) as? Cat
let cat4 = model(from: jsonString, type: type) as? Cat

JSONData

// jsonData也可以是NSData、NSMutableData类型
let jsonData = """
{
    "name": "Miaomiao",
    "weight": 6.66
}
""".data(using: .utf8)!

// 跟JSON的用法是一样的
let cat1 = jsonData.kj.model(Cat.self)
let cat2 = model(from:jsonData, Cat.self)

var type: Convertible.Type = Cat.self
let cat3 = jsonData.kj.model(type: type) as? Cat
let cat4 = model(from: jsonData, type: type) as? Cat

Model嵌套1

// 让需要进行转换的模型都遵守`Convertible`协议

struct Book: Convertible {
    var name: String = ""
    var price: Double = 0.0
}

struct Car: Convertible {
    var name: String = ""
    var price: Double = 0.0
}

struct Dog: Convertible {
    var name: String = ""
    var age: Int = 0
}

struct Person: Convertible {
    var name: String = ""
    var car: Car?
    var books: [Book]?
    var dogs: [String: Dog]?
}

let json: [String: Any] = [
    "name": "Jack",
    "car": ["name": "BMW7", "price": 105.5],
    "books": [
        ["name": "Fast C++", "price": 666.6],
        ["name": "Data Structure And Algorithm", "price": 1666.6]
    ],
    "dogs": [
        "dog0": ["name": "Larry", "age": 5],
        "dog1": ["name": "ErHa", "age": 2]
    ]
]

// 也是如此简单，不用再做额外的操作
let person = json.kj.model(Person.self)
XCTAssert(person.car?.name == "BMW7")
XCTAssert(person.books?[1].name == "Data Structure And Algorithm")
XCTAssert(person.dogs?["dog0"]?.name == "Larry")

Model嵌套2

// Set也能像Array那样支持Model嵌套

// Set要求存放的元素遵守Hashable协议
struct Book: Convertible, Hashable {
    var name: String = ""
    var price: Double = 0.0
}

struct Person: Convertible {
    var name: String = ""
    var books: Set<Book>?
}

let json: [String: Any] = [
    "name": "Jack",
    "books": [
        ["name": "Fast C++", "price": 666.6]
    ]
]

let person = json.kj.model(Person.self)
XCTAssert(person.name == "Jack")

XCTAssert(person.books?.count == 1)
// 从Set中取出来是个Book模型
let book = person.books?.randomElement()
XCTAssert(book?.name == "Fast C++")
XCTAssert(book?.price == 666.6)

Model嵌套3

struct Car: Convertible {
    var name: String = ""
    var price: Double = 0.0
}

class Dog: Convertible {
    var name: String = ""
    var age: Int = 0
    required init() {}
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
}

struct Person: Convertible {
    var name: String = ""
    // 如果你的模型有默认值，KakaJSON内部不会再创建新的模型
    // 会直接重复利用你创建的模型，节省内存分配和初始化的开销
    var car: Car = Car(name: "Bently", price: 106.5)
    var dog: Dog = Dog(name: "Larry", age: 5)
}

let json: [String: Any] = [
    "name": "Jake",
    "car": ["price": 305.6],
    "dog": ["name": "Wangwang"]
]

let person = json.kj.model(Person.self)
XCTAssert(person.name == "Jake")
// 保留默认值
XCTAssert(person.car.name == "Bently")
// 从json解析过来的值
XCTAssert(person.car.price == 305.6)
// 从json解析过来的值
XCTAssert(person.dog.name == "Wangwang")
// 保留默认值
XCTAssert(person.dog.age == 5)

递归

class Person: Convertible {
    var name: String = ""
    var parent: Person?
    required init() {}
}

let json: [String: Any] = [
    "name": "Jack",
    "parent": ["name": "Jim"]
]

let person = json.kj.model(Person.self)
XCTAssert(person.name == "Jack")
XCTAssert(person.parent?.name == "Jim")

泛型

struct NetResponse<Element>: Convertible {
    let data: Element? = nil
    let msg: String = ""
    private(set) var code: Int = 0
}

struct User: Convertible {
    let id: String = ""
    let nickName: String = ""
}

struct Goods: Convertible {
    private(set) var price: CGFloat = 0.0
    let name: String = ""
}

let json1 = """
{
    "data": {"nickName": "KaKa", "id": 213234234},
    "msg": "Success",
    "code" : 200
}
"""
let response1 = json1.kj.model(NetResponse<User>.self)
XCTAssert(response1?.msg == "Success")
XCTAssert(response1?.code == 200)
XCTAssert(response1?.data?.nickName == "KaKa")
XCTAssert(response1?.data?.id == "213234234")

let json2 = """
{
    "data": [
        {"price": "6199", "name": "iPhone XR"},
        {"price": "8199", "name": "iPhone XS"},
        {"price": "9099", "name": "iPhone Max"}
    ],
    "msg": "Success",
    "code" : 200
}
"""
let response2 = json2.kj.model(NetResponse<[Goods]>.self)
XCTAssert(response2?.msg == "Success")
XCTAssert(response2?.code == 200)
XCTAssert(response2?.data?.count == 3)
XCTAssert(response2?.data?[0].price == 6199)
XCTAssert(response2?.data?[0].name == "iPhone XR")
XCTAssert(response2?.data?[1].price == 8199)
XCTAssert(response2?.data?[1].name == "iPhone XS")
XCTAssert(response2?.data?[2].price == 9099)
XCTAssert(response2?.data?[2].name == "iPhone Max")

Model数组

struct Car: Convertible {
    var name: String = ""
    var price: Double = 0.0
}

// json数组可以是Array<[String: Any]>、NSArray、NSMutableArray
let json: [[String: Any]] = [
    ["name": "Benz", "price": 98.6],
    ["name": "Bently", "price": 305.7],
    ["name": "Audi", "price": 64.7]
]

// 调用json数组的modelArray方法即可
let cars = json.kj.modelArray(Car.self)
XCTAssert(cars[1].name == "Bently")

// 同样的还有其他方式
let cars2 = modelArray(from: json, Car.self)
var type: Convertible.Type = Car.self
let cars3 = json.kj.modelArray(type: type) as? [Car]
let cars4 = modelArray(from: json, type: type) as? [Car]

// 另外，jsonString转为Model数组，也是如此简单
let jsonString = "...."
let cars5 = jsonString.kj.modelArray(Car.self)
let cars6 = modelArray(from: jsonString, Car.self)
let cars7 = jsonString.kj.modelArray(type: type) as? [Car]
let cars8 = modelArray(from: jsonString, type: type) as? [Car]

字典嵌套Model数组

struct Book: Convertible {
    var name: String = ""
    var price: Double = 0.0
}

struct Person: Convertible {
    var name: String = ""
    var books: [String: [Book?]?]?
}

let name = "Jack"
let mobileBooks = [
    (name: "iOS", price: 10.5),
    (name: "Android", price: 8.5)
]
let serverBooks = [
    (name: "Java", price: 20.5),
    (name: "Go", price: 18.5)
]

let json: [String: Any] = [
    "name": name,
    "books": [
        "mobile": [
            ["name": mobileBooks[0].name, "price": mobileBooks[0].price],
            ["name": mobileBooks[1].name, "price": mobileBooks[1].price]
        ],
        "server": [
            ["name": serverBooks[0].name, "price": serverBooks[0].price],
            ["name": serverBooks[1].name, "price": serverBooks[1].price]
        ]
    ]
]

let person = json.kj.model(Person.self)
XCTAssert(person.name == name)
let books0 = person.books?["mobile"]
XCTAssert(books0??.count == mobileBooks.count)
for i in 0..<mobileBooks.count {
    XCTAssert(books0??[i]?.name == mobileBooks[i].name);
    XCTAssert(books0??[i]?.price == mobileBooks[i].price);
}
let books1 = person.books?["server"]
XCTAssert(books1??.count == serverBooks.count)
for i in 0..<serverBooks.count {
    XCTAssert(books1??[i]?.name == serverBooks[i].name);
    XCTAssert(books1??[i]?.price == serverBooks[i].price);
}

Convert

// 如果你想把JSON数据转换到原本已经创建好的模型实例上，可以使用convert方法

struct Cat: Convertible {
    var name: String = ""
    var weight: Double = 0.0
}

let json: [String: Any] = [
    "name": "Miaomiao",
    "weight": 6.66
]

var cat = Cat()
// .kj_m是.kj的mutable版本，牵扯到修改实例本身都是.kj_m开头
cat.kj_m.convert(json)
XCTAssert(cat.name == "Miaomiao")
XCTAssert(cat.weight == 6.66)

监听

// 有时候可能想在JSON转模型之前、之后做一些额外的操作
// KakaJSON会在JSON转模型之前调用模型的kj_willConvertToModel方法
// KakaJSON会在JSON转模型之后调用模型的kj_didConvertToModel方法

struct Car: Convertible {
    var name: String = ""
    var age: Int = 0

    mutating func kj_willConvertToModel(from json: [String: Any]) {
        print("Car - kj_willConvertToModel")
    }

    mutating func kj_didConvertToModel(from json: [String: Any]) {
        print("Car - kj_didConvertToModel")
    }
}

let name = "Benz"
let age = 100
let car = ["name": name, "age": age].kj.model(Car.self)
// Car - kj_willConvertToModel
// Car - kj_didConvertToModel
XCTAssert(car.name == name)
XCTAssert(car.age == age)

/*************************************************************/

// 同样也支持类
class Person: Convertible {
    var name: String = ""
    var age: Int = 0
    required init() {}

    func kj_willConvertToModel(from json: [String: Any]) {
        print("Person - kj_willConvertToModel")
    }

    func kj_didConvertToModel(from json: [String: Any]) {
        print("Person - kj_didConvertToModel")
    }
}

class Student: Person {
    var score: Int = 0

    override func kj_willConvertToModel(from json: [String: Any]) {
        // 如果有必要的话，可以调用super的实现
        super.kj_willConvertToModel(from: json)

        print("Student - kj_willConvertToModel")
    }

    override func kj_didConvertToModel(from json: [String: Any]) {
        // 如果有必要的话，可以调用super的实现
        super.kj_didConvertToModel(from: json)

        print("Student - kj_didConvertToModel")
    }
}

let name = "jack"
let age = 10
let score = 100
let student = ["name": name, "age": age, "score": score].kj.model(Student.self)
// Person - kj_willConvertToModel
// Student - kj_willConvertToModel
// Person - kj_didConvertToModel
// Student - kj_didConvertToModel
XCTAssert(student.name == name)
XCTAssert(student.age == age)
XCTAssert(student.score == score)