In my app I am using MVVM pattern. Below is my Model.

    struct NewsModel: Codable {
    let status: String
    let totalResults: Int
    let articles: [Article]
}

struct Article: Codable {
    let source: Source
    let author: String?
    let title: String
    let articleDescription: String?
    let url: String
    let urlToImage: String?
    let publishedAt: Date
    let content: String?
    
    enum CodingKeys: String, CodingKey {
        case source, author, title
        case articleDescription = "description"
        case url, urlToImage, publishedAt, content
    }
}

struct Source: Codable {
    let id: String?
    let name: String
}

Below is my ViewModel. Which is used for show the data from API.

   struct NewsArticleViewModel {
    
    let news: NewsModel
    let article: Article

    var title:String {
        return self.article.title
    }
    
    var publication:String {
        return self.article.articleDescription!
    }

    var imageURL:String {
        return self.article.urlToImage!
    }
}

Below is my API request class.

   class Webservice {
    
    func getTopNews(completion: @escaping (([NewsModel]?) -> Void)) {
        
        guard let url = URL(string: "https://newsapi.org/v2/top-headlines?country=us&category=business&apiKey=2bfee85c94e04fc998f65db51ec540bb") else {
            fatalError("URL is not correct!!!")
        }
        
        URLSession.shared.dataTask(with: url) {
            data, response, error in
            
            guard let data = data, error == nil else {
                DispatchQueue.main.async {
                    completion(nil)
                }
                return
            }
            let news = try? JSONDecoder().decode([NewsModel].self, from: data)
            DispatchQueue.main.async {
                completion(news)
            }
        }.resume()
    }
}

After receiving response from my API I want to show it on screen. For this I added below ViewModel.

    class NewsListViewModel: ObservableObject {
    
    @Published var news: [NewsArticleViewModel] = [NewsArticleViewModel]()
    
    func load() {
        fetchNews()
    }
    
    private func fetchNews() {
        Webservice().getTopNews {
            news in
            
            if let news = news {
                
//How to bind this data to NewsArticleViewModel and show it on UI?
            }
        }
    }
}

Please let me know. What I have to write there for showing it on UI.

CodePudding user response：

According to the documentation of newsapi.org your request will return one NewsModel object not an array. So change your Webservice class to:

class Webservice {
    //Change the completion handler to return an array of Article
    func getTopNews(completion: @escaping (([Article]?) -> Void)) {
        
        guard let url = URL(string: "https://newsapi.org/v2/top-headlines?country=us&category=business&apiKey=2bfee85c94e04fc998f65db51ec540bb") else {
            fatalError("URL is not correct!!!")
        }
        
        URLSession.shared.dataTask(with: url) {
            data, response, error in
            
            guard let data = data, error == nil else {
                DispatchQueue.main.async {
                    completion(nil)
                }
                return
            }
            // decode to a single NewsModel object instead of an array
            let decoder = JSONDecoder()
            decoder.dateDecodingStrategy = .iso8601

            let news = try? decoder.decode(NewsModel.self, from: data)
            DispatchQueue.main.async {
                // completion with an optional array of Article
                completion(news?.articles)
            }
        }.resume()
    }
}

You would need to map those received values to NewsArticleViewModel types. For example:

Webservice().getTopNews { articles in
      if let articles = articles {
            self.news = articles.map{NewsArticleViewModel(article: $0)}
      }
}

And remove let news: NewsModel from the NewsArticleViewModel struct as it is not needed.

Edit:

It seems:

let publishedAt: Date

is throwing an error. Jsondecoder fails to interpret the string to a date. Change your Webservice. I´ve updated it in my answer.

CodePudding user response：

You could remove the legacy MVVM pattern and do it in proper SwiftUI like this:

struct ContentView: View {
    @State private var articles = [Article]()

    var body: some View {
        NavigationView {
            List(articles) { article in
                Text(article.title)
            }
            .navigationTitle("Articles")
        }
        .task {
            do {
                let url = URL(string: "https://newsapi.org/v2/top-headlines?country=us&category=business&apiKey=2bfee85c94e04fc998f65db51ec540bb")!
                let (data, _) = try await URLSession.shared.data(from: url)
                articles = try JSONDecoder().decode([Article].self, from: data)
            } catch {
                articles = []
            }
        }
    }
}