解析json xcode swift 4

Question

问题。我想从这里解析 json 并在表格视图上显示，我使用的是 swift 4 和 Decodable。但我收到类型不匹配错误。 json链接：

https://newsapi.org/v2/top-headlines?sources=techcrunch&apiKey=50fb91212a47432d802b3b1ac0f717a3

我的结构看起来像这样。

    struct Root : Decodable {
    let status : String
//  let totalResults : Int
    let articles : [Article]
}

struct Article : Decodable {
    let source: Source
    let author, title, description: String
    let url: URL
//  let publishedAt: Date
    let urlToImage: String
}

struct Source: Decodable {
    let id, name: String
}

我的 ViewDidLoad 看起来像这样：

  var articles : [Article]? = []

    override func viewDidLoad() {
        super.viewDidLoad()
        tableview.delegate = self
        tableview.dataSource = self
        fetchArticles()
    }

    func fetchArticles(){
    let jsonURLString = "https://newsapi.org/v2/top-headlines?sources=techcrunch&apiKey=50fb91212a47432d802b3b1ac0f717a3"
    guard let url = URL(string: jsonURLString) else { return }
      URLSession.shared.dataTask(with: url) { (data,response,err) in
           guard let data = data else { return }
            self.myArticles = [Article]()
            do{
                let decoder = JSONDecoder()
                decoder.dataDecodingStrategy = .base64
                let root = try decoder.decode(Root.self, from: data)
                self.myArticles = root.articles
                DispatchQueue.main.async {
                    self.tableview.reloadData()
                }
            } catch let error{
                print(error)
            }
        }.resume()
}

我的 cellForRowAtIndexPath

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let myCell = tableView.dequeueReusableCell(withIdentifier: "articleCell", for: indexPath) as! ArticleCell

    let article = self.myArticles[indexPath.row]
    myCell.title.text = article.title
    myCell.body.text = article.description
    myCell.author.text = article.author
    myCell.imgView.downloadImage(from: ("https://tctechcrunch2011.files.wordpress.com/2017/04/uber-vs-waymo.png"))

    return myCell
}

我遇到了错误。

No errors, nothing loads to the table view.

Answer 1

错误很明显。您将解码一个数组，但对象是一个字典。

这会将 JSON 解码，包括对 URL 和 Date 的特殊解码。

根对象是字典，键 articles 包含文章，source 是字典，而不是数组

struct Root : Decodable {
    let status : String
    let articles : [Article]
}

struct Article : Decodable {
    let source: Source
    let author, title, description: String
    let url: URL
    let publishedAt: Date
    let urlToImage: String
}

struct Source: Decodable {
    let id, name: String
}

---

var articles = [Article]()

---

do {
   let decoder = JSONDecoder()
   decoder.dateDecodingStrategy = .iso8601
   let root = try JSONDecoder().decode(Root.self, from: data)
   self.articles = root.articles
   DispatchQueue.main.async {
      self.tableview.reloadData()
   }
} catch { print(error) }

不需要使用继承自NSObject的类

并且不要将数据源对象声明为可选并在cellForRow 中多次获取相同的项目，它是indexPath.row

 ...
 let article = self.articles[indexPath.row]
 myCell.title.text = article.title
 myCell.body.text = article.description
 myCell.author.text = article.author
 ...