Styjun

I am getting an error when decoding JSON in swift 4.2

Expected to decode Array but found a dictionary instead.

My JSON Model:

public struct NewsSource: Equatable, Decodable 

public let id: String?
public let name: String?
public let sourceDescription: String?
public let url: URL?

enum CodingKeys: String, CodingKey 
 case id
 case name
 case sourceDescription = "description"
 case url



public init(id: String,
 name: String,
 sourceDescription: String,
 url: URL,
 category: NewsCategory,
 language: NewsLanguage,
 country: NewsCountry) 
 self.id = id
 self.name = name
 self.sourceDescription = sourceDescription
 self.url = url
 

How I fetch the JSON:

func fetchJSON() 

let urlString = "https://newsapi.org/v2/sources?apiKey=myAPIKey"

guard let url = URL(string: urlString) else return 
 URLSession.shared.dataTask(with: url) (data, _, err) in
 DispatchQueue.main.async 
 if let err = err 
 print("Failed to get data from url:", err)
 return
 

 guard let data = data else return 
 print(data)
 do 

 let decoder = JSONDecoder()
 decoder.keyDecodingStrategy = .convertFromSnakeCase

 self.Sources = try decoder.decode([NewsSource].self, from: data)
 self.tableView.reloadData()

 catch let jsonErr 
 print("Failed to decode:", jsonErr)
 
 
 .resume()

If you look at the JSON that is being returned it looks like this:

{
 "status": "ok",
 "sources": [
 "id": "abc-news",
 "name": "ABC News",
 "description": "Your trusted source for breaking news, analysis, exclusive interviews, headlines, and videos at ABCNews.com.",
 "url": "https://abcnews.go.com",
 "category": "general",
 "language": "en",
 "country": "us"
 , 
 "id": "abc-news-au",
 "name": "ABC News (AU)",
 "description": "Australia's most trusted source of local, national and world news. Comprehensive, independent, in-depth analysis, the latest business, sport, weather and more.",
 "url": "http://www.abc.net.au/news",
 "category": "general",
 "language": "en",
 "country": "au"
 , 
 ...

While there is an array of sources, the array is not the root. The root of the JSON is an object with a status string and and a sources array. This is why the decoder is failing.

You need to define an additional struct to handle this:

struct NewsResult 
 let status: String
 let sources: [NewsSource]

Then you decode this object:

let sourceResult = try decoder.decode(NewsResult.self, from: data)
self.sources = sourceResult.sources

This should be your structure:

struct NewsSource: Codable 
 let status: String
 let sources: [NewsSource]


public struct NewsSource: Equatable, Decodable 

public let id: String?
public let name: String?
public let sourceDescription: String?
public let url: URL?

enum CodingKeys: String, CodingKey 
 case id
 case name
 case sourceDescription = "description"
 case url



public init(id: String,
 name: String,
 sourceDescription: String,
 url: URL,
 category: NewsCategory,
 language: NewsLanguage,
 country: NewsCountry) 
 self.id = id
 self.name = name
 self.sourceDescription = sourceDescription
 self.url = url
 

struct Source: Codable 
 let id, name, description: String
 let url: String
 let category: Category
 let language, country: String


enum Category: String, Codable 
 case business = "business"
 case entertainment = "entertainment"
 case general = "general"
 case health = "health"
 case science = "science"
 case sports = "sports"
 case technology = "technology"

And then to decode it:

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let newsSource = try? decoder.decode(NewsSource.self, from: data)
self.Sources = newsSource.sources
self.tableView.reloadData()

Hope this helps!