如何解码来自 URLSession 的 http 响应数据并映射到响应结构 swift
How to decode an http response data from URLSession and map to a response structure swift
我是 swift 编程的新手..能够从 URLSession 获得成功的响应,但我无法将数据对象解析(解码)为我想要的 APIResponse 结构
这是我的url请求代码:
func load(urlRequest: URLRequest, withCompletion completion: @escaping (_ response: APIResponse) -> Void) {
let task = URLSession.shared.dataTask(with: urlRequest) { (data, response, error) in
guard error == nil else {
print("Error fetching data from server\nERROR: \(String(describing: error))")
return
}
guard let jsonData = data else {
print("Response Data is empty")
return
}
printResponseBody(response: data)
let decoder = JSONDecoder()
let response = try? decoder.decode(APIResponse.self, from: jsonData)
guard let decodedResponse = response else {
print("Unable to parse data from response")
return
}
print("Decoded Response: ", decodedResponse)
DispatchQueue.main.async { completion(decodedResponse) }
}
task.resume()
}
这是我的响应结构,我需要将响应数据映射到该结构以在我的代码中使用:
struct APIResponse: Codable {
let responseCode: Int
let data: ResultSet
let meta: Meta
enum CodingKeys: String, CodingKey {
case responseCode = "response_code"
case data, meta
}
}
// MARK: - DataClass
struct ResultSet: Codable {
let appVersionUpdate: String
let offers: [Offer]
let rate: Int
enum CodingKeys: String, CodingKey {
case appVersionUpdate = "app_version_update"
case offers, rate
}
}
// MARK: - Offer
struct Offer: Codable, Identifiable {
let id: Int
let title: String
let image: String?
let r, resultCount: Double
enum CodingKeys: String, CodingKey {
case id, r = "r"
case title, image
case resultCount = "result_count"
}
}
// MARK: - Meta
struct Meta: Codable {
let apiVersion: Int
enum CodingKeys: String, CodingKey {
case apiVersion = "api_version"
}
这是我要解码的来自服务器的json
{
"response_code": 0,
"data": {
"app_version_update": "",
"offers": [
{
"title": "Special Scheme1",
"image": "http://59.145.109.138:11101/Offers/BGL_banner_1080_x_540_1.jpg",
"r": 1.0,
"result_count": 5.0
},
{
"title": "test 1",
"image": "http://59.145.109.138:11101/Offers/Yoho-National-Park2018-10-27_10-10-52-11.jpg",
"r": 2.0,
"result_count": 5.0
},
{
"title": "Offer Test 1234444",
"image": "http://59.145.109.138:11101/Offers/Stanley-Park2018-10-27_10-11-27-44.jpg",
"r": 3.0,
"result_count": 5.0
}
],
"rate": 2000
},
"meta": {
"api_version": 2.0
}
}
每当我 运行 此代码时,我都会收到“无法从响应中解析数据”错误。如果有人告诉我我在这里做错了什么,我将不胜感激
问题在于解码 Offer
中的 id
。用这个替换你的Offer
:
struct Offer: Codable, Identifiable {
let id: Int
let title: String
let image: String?
let r, resultCount: Int
enum CodingKeys: CodingKey {
case id, r, title, image, resultCount
var stringValue: String {
switch self {
case .id, .r: return "r"
case .title: return "title"
case .image: return "image"
case .resultCount: return "result_count"
}
}
}
}
备注
- 首先,你不应该摆脱这个错误。相反,您可以打印错误并尝试找出问题所在。
- 如果您声明
enum CodingKeys: String, CodingKey
,每种情况的原始值 必须 与其他情况不同,否则 Xcode 会报错。在你的例子中,它没有抱怨,因为 id
是 Identifiable
协议的要求,但它甚至没有使用你为 id
设置的原始值。如果你想对 2 个不同的变量使用相同的键,你应该做我上面做的同样的事情。
更好的代码
这将与您的代码一样工作,但更简洁:
struct Offer: Codable, Identifiable {
var id: Int { r }
let title: String
let image: String?
let r, resultCount: Int
enum CodingKeys: String, CodingKey {
case r, title, image, resultCount
}
}
它基本上说每当你需要 id
时,从 r
获取它。你也可以像我一样去掉CodingKeys
中的stringValue
,改用CodingKeys: String
构象。
我是 swift 编程的新手..能够从 URLSession 获得成功的响应,但我无法将数据对象解析(解码)为我想要的 APIResponse 结构
这是我的url请求代码:
func load(urlRequest: URLRequest, withCompletion completion: @escaping (_ response: APIResponse) -> Void) {
let task = URLSession.shared.dataTask(with: urlRequest) { (data, response, error) in
guard error == nil else {
print("Error fetching data from server\nERROR: \(String(describing: error))")
return
}
guard let jsonData = data else {
print("Response Data is empty")
return
}
printResponseBody(response: data)
let decoder = JSONDecoder()
let response = try? decoder.decode(APIResponse.self, from: jsonData)
guard let decodedResponse = response else {
print("Unable to parse data from response")
return
}
print("Decoded Response: ", decodedResponse)
DispatchQueue.main.async { completion(decodedResponse) }
}
task.resume()
}
这是我的响应结构,我需要将响应数据映射到该结构以在我的代码中使用:
struct APIResponse: Codable {
let responseCode: Int
let data: ResultSet
let meta: Meta
enum CodingKeys: String, CodingKey {
case responseCode = "response_code"
case data, meta
}
}
// MARK: - DataClass
struct ResultSet: Codable {
let appVersionUpdate: String
let offers: [Offer]
let rate: Int
enum CodingKeys: String, CodingKey {
case appVersionUpdate = "app_version_update"
case offers, rate
}
}
// MARK: - Offer
struct Offer: Codable, Identifiable {
let id: Int
let title: String
let image: String?
let r, resultCount: Double
enum CodingKeys: String, CodingKey {
case id, r = "r"
case title, image
case resultCount = "result_count"
}
}
// MARK: - Meta
struct Meta: Codable {
let apiVersion: Int
enum CodingKeys: String, CodingKey {
case apiVersion = "api_version"
}
这是我要解码的来自服务器的json
{
"response_code": 0,
"data": {
"app_version_update": "",
"offers": [
{
"title": "Special Scheme1",
"image": "http://59.145.109.138:11101/Offers/BGL_banner_1080_x_540_1.jpg",
"r": 1.0,
"result_count": 5.0
},
{
"title": "test 1",
"image": "http://59.145.109.138:11101/Offers/Yoho-National-Park2018-10-27_10-10-52-11.jpg",
"r": 2.0,
"result_count": 5.0
},
{
"title": "Offer Test 1234444",
"image": "http://59.145.109.138:11101/Offers/Stanley-Park2018-10-27_10-11-27-44.jpg",
"r": 3.0,
"result_count": 5.0
}
],
"rate": 2000
},
"meta": {
"api_version": 2.0
}
}
每当我 运行 此代码时,我都会收到“无法从响应中解析数据”错误。如果有人告诉我我在这里做错了什么,我将不胜感激
问题在于解码 Offer
中的 id
。用这个替换你的Offer
:
struct Offer: Codable, Identifiable {
let id: Int
let title: String
let image: String?
let r, resultCount: Int
enum CodingKeys: CodingKey {
case id, r, title, image, resultCount
var stringValue: String {
switch self {
case .id, .r: return "r"
case .title: return "title"
case .image: return "image"
case .resultCount: return "result_count"
}
}
}
}
备注
- 首先,你不应该摆脱这个错误。相反,您可以打印错误并尝试找出问题所在。
- 如果您声明
enum CodingKeys: String, CodingKey
,每种情况的原始值 必须 与其他情况不同,否则 Xcode 会报错。在你的例子中,它没有抱怨,因为id
是Identifiable
协议的要求,但它甚至没有使用你为id
设置的原始值。如果你想对 2 个不同的变量使用相同的键,你应该做我上面做的同样的事情。
更好的代码
这将与您的代码一样工作,但更简洁:
struct Offer: Codable, Identifiable {
var id: Int { r }
let title: String
let image: String?
let r, resultCount: Int
enum CodingKeys: String, CodingKey {
case r, title, image, resultCount
}
}
它基本上说每当你需要 id
时,从 r
获取它。你也可以像我一样去掉CodingKeys
中的stringValue
,改用CodingKeys: String
构象。