Swift4中使用URLSession和JSONDecode丢失数据

本文介绍了Swift4中使用URLSession和JSONDecode丢失数据的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

使用Swift4，iOS11.1，Xcode9.1，

Using Swift4, iOS11.1, Xcode9.1,

以下parseData方法几乎可以正常工作。一切似乎都可以正常工作（此URLSession和JSONDecode可以获取正确的JSON数据集）。

The following parseData method almost works. Everything seems to work fine (and a correct JSON-data set is fetched by this URLSession and JSONDecode).

但是，真正令我惊讶的是正常的浏览器显示不同的JSON数据（即，与该iOS-URLSession方法相比，获取的数据是其20倍）。为什么？??

However, what is really surprising to me is the fact that a normal Browser shows different JSON-data (i.e. 20x as much is fetched than compared to this iOS-URLSession approach). Why is that ??

在下面的代码中，您可以找到两个打印语句。第一个显示实际的URLRequest字符串（包括所有查询和类型参数）。第二个打印出获取的JSON数据集的数量。

In the code below, you can find two print statements. The first showing the actual URLRequest-string (including all query- and type-parameters). The second prints the number of fetched JSON data-sets.

如果您使用浏览器并使用完全相同的URLRequest-string获取JSON，则数据集的数量为20套。有了URLSession，它只有1套

If you use a Browser and fetch the JSON with the exact same URLRequest-string, then the number of datasets is 20 sets. With the URLSession it is only 1 set

为什么传递的JSON数据长度存在这种差异？?????????

Why this difference in JSON data-length delivered ??????????

这里是PRINT_LOG 1：

Here is PRINT_LOG 1 :

maps.googleapis/maps/api/place/textsearch/json?query=Cham,%20Langackerstrasse&type=bus_station&key=AIzaSyDYtkKiJRuJ9tjkeOtEAuEtTLp5a0XR1M0 (API key no longer valid - after having found the solution, I did change the API-key for security reasons. The Question and its Answer are still of value tough).

这里是PRINT_LOG 2：

Here is PRINT_LOG 2 :

count = 1

这是我的代码：

func parseData(queryString: String) { // nested function func createURLWithComponents() -> URL? { let urlComponents = NSURLComponents() urlComponents.scheme = "https"; urlComponents.host = "maps.googleapis"; urlComponents.path = "/maps/api/place/textsearch/json"; // add params urlComponents.queryItems = [ URLQueryItem(name: "query", value: "Cham, Langackerstrasse"), URLQueryItem(name: "type", value: "bus_station"), URLQueryItem(name: "key", value: AppConstants.GOOGLE_MAPS_DIRECTIONS_API_KEY) ] return urlComponents.url } let myUrl = createURLWithComponents() var myRequest = URLRequest(url: myUrl!) myRequest.httpMethod = "GET" myRequest.setValue("application/json; charset=UTF-8", forHTTPHeaderField: "Content-Type") let myConfiguration = URLSessionConfiguration.default let session = URLSession(configuration: myConfiguration, delegate: nil, delegateQueue: OperationQueue.main) // Until here everything all right !!!!!!!!!!!!!!!!!!!!!!!!!!!!! // i.e. the following print is correct !!!!!!!!!!!!!!!!!!!!!!!!! // (and when this print is copied to a Browser then the data fetched has 20 JSON-entries...) // PRINT_LOG 1 print(myRequest.description) let myTask = session.dataTask(with: myRequest) { (data, response, error) in if (error != nil) { print("Error1 fetching JSON data") } else { do { //Decode retrived data with JSONDecoder and assing type of Station object let stationData = try JSONDecoder().decode(Station.self, from: data!) // Here is the puzzling thing to happen !!!!!!!!!!!!!!!!!!!!!! // i.e. the following print reveals count = 1 !!!!!!!!!!!!!!!!! // ??? Why not 20 as with the Browser ???????????????????? // PRINT_LOG 2 print("count = " + "\(String(describing: stationData.results.count))") } catch let error { print(error) } } } myTask.resume() }

为完整起见，以下是匹配的结构：

For completeness, here is the matching Struct:

struct Station: Codable { let htmlAttributions: [String] let nextPageToken: String? let results: [Result] let status: String struct Result: Codable { let formattedAddress: String let geometry: Geometry let icon: String let id: String let name: String let photos: [Photo]? let placeID: String let rating: Double? let reference: String let types: [String] struct Geometry: Codable { let location: Coordinates let viewport: Viewport struct Coordinates: Codable { let lat: Double let lng: Double init(from decoder: Decoder) throws { let values = try decoder.container(keyedBy: CodingKeys.self) lat = try values.decode(Double.self, forKey: .lat) lng = try values.decode(Double.self, forKey: .lng) } enum CodingKeys : String, CodingKey { case lat case lng } } struct Viewport: Codable { let northeast: Coordinates let southwest: Coordinates enum CodingKeys : String, CodingKey { case northeast case southwest } } enum CodingKeys : String, CodingKey { case location case viewport } } struct Photo: Codable { let height: Int let htmlAttributions: [String] let photoReference: String? let width: Int enum CodingKeys : String, CodingKey { case height case htmlAttributions = "html_attributions" case photoReference = "photo_reference" case width } } enum CodingKeys : String, CodingKey { case formattedAddress = "formatted_address" case geometry case icon case id case name case photos case placeID = "place_id" case rating case reference case types } } enum CodingKeys : String, CodingKey { case htmlAttributions = "html_attributions" case nextPageToken = "next_page_token" case results case status } }

感谢f或对此有任何帮助。

Thanks for any help on this.

推荐答案

找到了!!!

这是缺少的Info.plist本地化！ （即，我在运行->选项->应用语言下运行了将语言设置为德语的应用程序表单XCode）。我的Info.plist只是部分本地化（即，我的文件 InfoPlist.strings 仅有几个条目，但没有完整的翻译）。而缺少的翻译会导致此问题!!!!

It was the missing Info.plist localization ! (i.e. I ran the App form XCode having the Language set to German under Run-->Options-->Appliation Language). My Info.plist was only partly localized (i.e. My file InfoPlist.strings had only a few entries yet - but not a complete translation). And this missing translation lead to this problem !!!!

以纯英语运行它可以正常工作，并且我得到了20条预期的条目。

Running it in pure English works fine and I get 20 entries as expected.