Swift中JSON转model

1.Codeble

Swift中，可以使用Codable协议来将JSON转换为model。

public typealias Codable = Decodable & Encodable

Codable 是一个组合协议，由 Decodable 和 Encodable 两个协议组成。作用是将 JSON 转换为 model 对象，也可以反过来将 model 对象转换为 JSON 或其它格式。

let jsonString = """
    {
        "name": "davidlii",
        "email": "davidlii@sina.com",
        "sex":true,
        "age": 18
    }
"""
// JSON中的字段可以比实体中的属性多

struct User: Codable {
    let name: String
    let email: String
    let sex: Bool
}

do {
    //1.json转Model
    let data = jsonString.data(using: .utf8)!
    let usr = try JSONDecoder().decode(User.self, from: data)
    print(usr)
    
    //2.model转json
    let encodeData = try JSONEncoder().encode(usr)
    let json = String.init(data: encodeData, encoding: .utf8)
    print(json!)
    
}catch{
    print("~some error~")
}

2.映射

如果Model中的属性名与 JSON 中的键不一致，可使用CodingKeys枚举来映射。

let jsonString = """
    {
        "name": "davidlii",
        "email": "davidlii@sina.com",
        "sex":true,
    }
"""

struct User: Codable {
    let name: String
    let emailBox: String //与JSON中不匹配
    let sex: Bool
    
    //映射键与属性
    private enum CodingKeys :String, CodingKey{
        case name
        case emailBox = "email" //匹配不规则的JSON字段
        case sex
    }
}

do {
    //JSON转Model
    let data = jsonString.data(using: .utf8)!
    let usr = try JSONDecoder().decode(User.self, from: data)
    print(usr)
    
}catch{
    print("~some error~")
}

3.自定义编解码

JSON中字段的类型可能会与model中的不同，需要我们自定义编解码，来达到二者的统一：

let jsonString = """
{
    "name": "davidlii",
    "sex": 0,
}
"""

struct User: Codable {
    let name: String
    let sex: Bool
    
    //下面会用到
    private enum CodingKeys :String, CodingKey{
        case name
        case sex
    }
    //解码
    init(from decoder: Decoder) throws {
        let box = try decoder.container(keyedBy: CodingKeys.self)
        self.name = try box.decode(String.self, forKey: .name) //CodingKeys中定义的枚举
        //先取出来Int值
        let sexInt = try box.decode(Int.self, forKey: .sex)
        //再转换成Bool
        self.sex = (sexInt == 1)
    }
    //编码    
    func encode(to encoder: Encoder) throws {
        var box = encoder.container(keyedBy: CodingKeys.self)
        try box.encode(self.name, forKey: .name)
        // 编码成Int
        try box.encode(sex ? 1 : 0, forKey: .sex)
    }
}

do {
    //1.json转Model
    let data = jsonString.data(using: .utf8)!
    let usr = try JSONDecoder().decode(User.self, from: data)
    print(usr)
    
    //2.model转json
    let encodeData = try JSONEncoder().encode(usr)
    let json = String.init(data: encodeData, encoding: .utf8)
    print(json!)
    
}catch{
    print("~some error~")
}

4.数组属性

JSON中有数组类型时的处理：

let jsonString = """
{
    "id": 1,
    "users": [
        {
            "name": "davidlii",
            "email": "davidlii@sina.com",
            "sex":true,
        },
        {
            "name": "Het",
            "email": "Het@sina.com",
            "sex":false,
        }
    ]
}
"""

//小组
struct Group: Codable {
    let identifier: Int
    let users:[User] // 数组
    
    //映射键与属性
    private enum CodingKeys :String, CodingKey{
        case identifier = "id"
        case users
    }
}
//组员
struct User: Codable {
    let name: String
    let ema1l: String
    let sex: Bool
    
    //映射键与属性
    private enum CodingKeys :String, CodingKey{
        case name
        case ema1l = "email" //匹配不规则的JSON字段
        case sex
    }
}

do {
    //1.json转Model
    let data = jsonString.data(using: .utf8)!
    let usrs = try JSONDecoder().decode(Group.self, from: data)
    print(usrs)
    
    //2.model转json
    let encodeData = try JSONEncoder().encode(usrs)
    let json = String.init(data: encodeData, encoding: .utf8)
    print(json!)
    
}catch{
    print("~some error~")
}

5.可选属性

model中可选属性为空时，编码后不会包含在 JSON 数据中。解码时，JSON字段中可不传此字段。

let jsonString = """
{
    "users": [
        {
            "name": "davidlii",
            "email": "davidlii@sina.com",
            "sex":true,
            "age": 18
        },
        {
            "name": "Het",
            "email": "Het@sina.com",
            "sex":false,
        }
    ]
}
"""

//小组
struct Group: Codable {
    let users:[User]
}
//组员
struct User: Codable {
    let name: String
    let email: String
    let sex: Bool
    let age: Int?
}

do {
    //1.json转Model
    let data = jsonString.data(using: .utf8)!
    let usrs = try JSONDecoder().decode(Group.self, from: data)
    print(usrs)
    
    //2.model转json
    let encodeData = try JSONEncoder().encode(usrs)
    let json = String.init(data: encodeData, encoding: .utf8)
    print(json!)
    
}catch{
    print("~some error~")
}

输出的字符串：

{"users":[{"email":"davidlii@sina.com","sex":true,"age":18,"name":"davidlii"},{"name":"Het","email":"Het@sina.com","sex":false}]}

编码后，不会包含为nil的age字段。

---

相关参考：

#©