解码 JSON 响应

Question

我正在尝试从 JSON 响应中获取一些价格数据并将其保存在用户默认值中...

价格类别是：

  import Foundation

struct Prices : Decodable{
let id, id_service: Int
let nationality: String
let price: Int
let createdAt: String?
let updatedAt: String?
}

class Price : NSObject, NSCoding {
var id, id_service: Int
var nationality: String
var price: Int
var createdAt: String?
var updatedAt: String?


init(id: Int, id_service: Int, nationality: String, price: Int) {
    self.id = id
    self.id_service = id_service
    self.nationality = nationality
    self.price = price

}

required convenience init(coder aDecoder: NSCoder) {
    let id = aDecoder.decodeInteger(forKey: "id")
    let id_service = aDecoder.decodeInteger(forKey: "id_service")
    let nationality = aDecoder.decodeObject(forKey: "nationality") as! String
    let price = aDecoder.decodeInteger(forKey: "price")
    self.init(id: id, id_service: id_service, nationality: nationality, price: price)
}

func encode(with aCoder: NSCoder) {
    aCoder.encode(id, forKey: "id")
    aCoder.encode(id_service, forKey: "id_service")
    aCoder.encode(nationality, forKey: "nationality")
    aCoder.encode(price, forKey: "price")
}

}

我调用的方法是：

   func GetPrices() {

let todoEndpoint: String = "my link"
guard let url = URL(string: todoEndpoint) else {
    print("Error: cannot create URL")
    return
}
let urlRequest = URLRequest(url: url)

let config = URLSessionConfiguration.default
let session = URLSession(configuration: config)

let task = session.dataTask(with: urlRequest) {
    (data, response, error) in
    guard error == nil else {
        print("error calling GET on /public/api/services")
        print(error!)
        return
    }
    guard let responseData = data else {
        print("Error: did not receive data")
        return
    }
    do {

        let decoder = JSONDecoder()
        decoder.keyDecodingStrategy = .convertFromSnakeCase
        let prices1 = try decoder.decode([Prices].self, from: responseData)
        print("1")
        var prices = [Price]()
        for price in prices1{
            let newprice = Price(id: price.id, id_service: price.id_service,nationality: price.nationality, price: price.price)
            print("2")
            prices.append(newprice)
             print(newprice.nationality)
        }


        var userDefaults = UserDefaults.standard
        let encodedData: Data = NSKeyedArchiver.archivedData(withRootObject: prices)
        userDefaults.set(encodedData, forKey: "prices")
        userDefaults.synchronize()

        let decoded  = userDefaults.object(forKey: "prices") as! Data
        let decodedPrice = NSKeyedUnarchiver.unarchiveObject(with: decoded) as! [Price]

        for price in decodedPrice {
            print(price.nationality)
        }


    } catch  {
        print("error trying to convert data to JSON")
        return
    }
}
task.resume()
}

我拥有的 JSON 是这样的（它现在只有一个.. 但它是一个数组）：

[
{
    "id": 1,
    "id_service": 2,
    "nationality": "Phili",
    "price": 150,
    "created_at": "2018-04-23 11:43:40",
    "updated_at": "2018-04-23 11:43:40",
    "deleted_at": null
}
]

问题是我总是收到此消息：尝试将数据转换为 JSON 时出错

为什么？我做错了什么？如何解决？

Answer 1

您正在使用 .convertFromSnakeCase 进行解码，因此您的属性应该是驼峰式的。

decoder.keyDecodingStrategy = .convertFromSnakeCase

参考。 https://developer.apple.com/documentation/foundation/jsondecoder.keydecodingstrategy/2949105-convertfromsnakecase

所以要进行修复，请将您的属性名称 id_service 更改为 idService，如下所示。

struct Prices : Decodable{
    let id, idService: Int
    let nationality: String
    let price: Int
    let createdAt: String?
    let updatedAt: String?
}

为了更好地理解，您也可以查看 .useDefaultKeys https://developer.apple.com/documentation/foundation/jsondecoder.keydecodingstrategy/2949131-usedefaultkeys