Swift4: Codable->字典转模型的具体实现

一、字典转模型

• 现有如下JSON数据

let dict: [String : Any] = [
    "name" : "zhangsan",
    "height" : 1.88,
    "pet" : [
        "name" : "xiaohei",
        "age" : 3
    ],
    "picture": [
        [
            "url": "这里是url",
            "name": "一张图片"
        ],
        [
            "url": "这里是url",
            "name": "一张图片"
        ]
    ]
]

• 根据数据, 定义三个类: Person, Pet, Picture, 每个类都遵守Codable协议

class Person: Codable {
    var name: String?
    var age: Int?
    var h: Double?
    var pet: Pet?
    var picture: [Picture]?
    
    private enum CodingKeys: String, CodingKey {
        case h = "height"
        case name
        case age
        case pet
        case picture
    }
}

class Pet: Codable {
    var name: String?
    var age: Int?
}

class Picture: Codable {
    var url: String?
    var name: String?
}

• Person类中有如下代码, 表示属性h接收JSON数据中的height字段对应的值

    private enum CodingKeys: String, CodingKey {
        case h = "height"
        case name
        case age
        case pet
        case picture
    }

• 定义字典转模型方法, 这里使用了泛型

func JSONModel<T>(_ type: T.Type, withKeyValues data:[String:Any]) throws -> T where T: Decodable {
    let jsonData = try JSONSerialization.data(withJSONObject: data, options: [])
    let model = try JSONDecoder().decode(type, from: jsonData)
    return model
}

• 调用字典转模型方法

if let p = try? JSONModel(Person.self, withKeyValues: dict) {
    print(p.name, p.h, p.age)
    print(p.pet?.name, p.pet?.age)
    print(p.picture?.first?.url, p.picture?.first?.name)
}
// 控制台打印: 
Optional("zhangsan") Optional(1.8799999999999999) nil
Optional("xiaohei") Optional(3)
Optional("这里是url") Optional("一张图片")

这里类的所有属性都是可选类型, 这是因为当类中的属性, 在JSON数据中没有对应key时,
1、如果属性非可选, 就会转模型失败
2、如果属性可选, 这个属性就不会被赋值, 并且模型转换成功

二、数组转模型数组

• 现有如下JSON数组

let list: [[String:Any]] = [
    [
        "name" : "zhangsan",
        "age" : 20
    ],
    [
        "name" : "lisi",
        "age" : 18
    ],
    [
        "name" : "wangwu",
        "age" : 25
    ]
]

• 定义数组转模型数组方法

func JSONModels<T>(_ type: T.Type, withKeyValuesArray datas: [[String:Any]]) throws -> [T]  where T: Decodable {
    var temp: [T] = []
    for data in datas {
        let model = try JSONModel(type, withKeyValues: data)
        temp.append(model)
    }
    return temp
}

• 调用数组转模型数组方法

if let ps = try? JSONModels(Person.self, withKeyValuesArray: list) {
    for p in ps {
        print(p.name, p.age)
    }
}
// 控制台打印:
Optional("zhangsan") Optional(20)
Optional("lisi") Optional(18)
Optional("wangwu") Optional(25)

三、上面用到的两个方法

/// 字典 -> 模型
///
/// - Parameters:
///   - type: 类型
///   - data: 字典数据
/// - Returns: 模型结果
/// - Throws: 错误处理
func JSONModel<T>(_ type: T.Type, withKeyValues data:[String:Any]) throws -> T where T: Decodable {
    let jsonData = try JSONSerialization.data(withJSONObject: data, options: [])
    let model = try JSONDecoder().decode(type, from: jsonData)
    return model
}

/// 字典数组 -> 模型数组
///
/// - Parameters:
///   - type: 类型
///   - datas: 字典组数
/// - Returns: 模型数组结果
/// - Throws: 错误处理
func JSONModels<T>(_ type: T.Type, withKeyValuesArray datas: [[String:Any]]) throws -> [T]  where T: Decodable {
    var temp: [T] = []
    for data in datas {
        let model = try JSONModel(type, withKeyValues: data)
        temp.append(model)
    }
    return temp
}