[英]Trying to return a value from API with JSON
我试图从 newsapi.org/ 获取数据。
parseJSON 返回错误,由于某种原因它无法从 NewsData 获取数据。
我认为我的 NewsData 属性存在一些问题,其中 parseJSON func 无法找出数据。
这是 JSON(来自 urlString):
{
"status": "ok",
"totalResults": 38,
"articles": [
{
"source": {
"id": "fox-news",
"name": "Fox News"
},
"author": "Ryan Gaydos",
"title": "Errol Spence Jr. retains welterweight titles in victory over Danny Garcia - Fox News",
"description": "Errol Spence Jr. defeated Danny Garcia via unanimous decision Saturday night to retain the WBC and IBF welterweight titles.",
"url": "https://www.foxnews.com/sports/errol-spence-jr-danny-garcia-boxing-2020",
"urlToImage": "https://static.foxnews.com/foxnews.com/content/uploads/2020/12/Errol-Spence2.jpg",
"publishedAt": "2020-12-06T05:39:59Z",
"content": "Errol Spence Jr. defeated Danny Garcia via unanimous decision Saturday night to retain the WBC and IBF welterweight titles.\r\nThe judges scored the fight 116-112, 116-112, 117-111 in
favor of Spence.\r… [+1417 chars]"
}
]
}
这是我的代码:
新闻数据.Swift:
struct NewsData: Codable {
let articles: [Article]
}
struct Article: Codable {
let title: String
let description: String
let content: String
}
新闻经理.Swift:
func getNews() {
let urlString = "\(baseURL)&apiKey=\(apiKey)"
if let url = URL(string: urlString){
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { (data, response, error) in
if error != nil {
print(error)
} else {
if let safeData = data {
if let news = self.parseJSON(safeData) {
print(news)
}
}
}
}
task.resume()
}
}
func parseJSON(_ data: Data) -> String? {
let encoder = JSONDecoder()
do {
let encodedData = try encoder.decode(NewsData.self, from: data)
let des = encodedData.articles[0].content
let title = encodedData.articles[0].title
let content = encodedData.articles[0].content
return content
} catch {
print(error)
return nil
}
}
}
返回错误是:
valueNotFound(Swift.String, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "articles", intValue: nil), _JSONKey(stringValue: "Index 1", intValue: 1), CodingKeys(stringValue: "content", intValue: nil)], debugDescription: "Expected String value but found null instead.", underlyingError: nil))
DecodingError
是有史以来最精确和最容易理解的错误之一。
请完整阅读。
valueNotFound(Swift.String, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "articles", intValue: nil), _JSONKey(stringValue: "Index 1", intValue: 1), CodingKeys(stringValue: "content", intValue: nil)], debugDescription: “预期的字符串值,但找到了 null。”,underlyingError: nil))
有三个重要信息:
What : valueNotFound
表示某处缺少值
其中: CodingPath
类似于键路径,连接stringValue
的结果是:
articles[1].content
指向文章第二项中的属性内容
原因: debugDescription
描述了实际错误:
Expected
表示错误的类型 → 非可选String
found
表示正确的类型 → <null>
不是值,需要可选类型解决方案:将content
声明为可选
struct Article: Codable {
let title: String
let description: String
let content: String?
}
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