How to parse Wikipedia JSON Dictionary with Swift? - ios

Question

I'm new to the Wikipedia API and I have been trying to parse the image url from the API. The JSON I'm trying to parse is as follows:
API:
https://en.wikipedia.org/w/api.php?action=query&titles=tokyo&prop=pageimages&format=json
JSON Result:
{"batchcomplete": "",
"query": {
"normalized": [
{
"from": "tokyo",
"to": "Tokyo"
}
],
"pages": {
"30057": {
"pageid": 30057,
"ns": 0,
"title": "Tokyo",
"thumbnail": {
"source": "https://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Skyscrapers_of_Shinjuku_2009_January.jpg/50px-Skyscrapers_of_Shinjuku_2009_January.jpg",
"width": 50,
"height": 27
},
"pageimage": "Skyscrapers_of_Shinjuku_2009_January.jpg"
}
}
}
}
Below are the struct I created to parse the data. I can see the url when I print it to the console, but since "source" is nested under "thumbnail", which lives in the value of the [String:Page] dict pair, I can't figure out a way to access it. How do I parse data in a dictionary like this? Thank you for your help in advance.
struct WikiAPIResults: Codable {
let batchcomplete: String?
let query: Query?
}
struct Query: Codable {
let normalized: [Normalized]?
let pages: [String:Pages]? // <- I can get to here
}
struct Normalized: Codable {
let from, to: String?
}
struct Pages: Codable {
let pageid, ns: Int?
let title: String?
let thumbnail: Thumbnail?
let pageimage: String?
}
struct Thumbnail: Codable {
let source: String? // <- But I want to grab this
let width, height: Int?
}
func fetchImageFromWikipedia(imageKeyword: String, completion: #escaping (WikiAPIResults) -> Void) {
var urlComponents = URLComponents(string: "https://en.wikipedia.org/w/api.php?")!
urlComponents.queryItems = [
"action": "query",
"titles": imageKeyword,
"prop": "pageimages",
"format": "json"].map { URLQueryItem(name: $0.key, value: $0.value) }
let task = URLSession.shared.dataTask(with: urlComponents.url!) { data, response, error in
let jsonDecoder = JSONDecoder()
if let data = data,
let result = try? jsonDecoder.decode(WikiAPIResults.self, from: data) {
completion(result)
}
}
task.resume()
}
fetchImageFromWikipedia(imageKeyword: "Tokyo") { result in
print(result.query?.pages?.values)
}

Answer 1

Do you mean gathering all thumbnail sources?
fetchImageFromWikipedia(imageKeyword: "Tokyo") { result in
let pages = result.query?.pages?.compactMap { $0.value } ?? []
let thumbnailSources = pages.compactMap { $0.thumbnail?.source }
print(thumbnailSources)
}

Answer 2

This works with your example perfectly:
import Foundation
struct Response: Decodable {
struct Query: Decodable {
struct NormalizedQuery: Decodable {
let from: String
let to: String
}
struct Page: Decodable {
struct Thumbnail: Decodable {
let source: URL
let width: Int
let height: Int
}
let id: Int
let ns: Int
let title: String
let thumbnail: Thumbnail
let pageImage: String
private enum CodingKeys: String, CodingKey {
case id = "pageid"
case ns
case title
case thumbnail
case pageImage = "pageimage"
}
}
let normalized: [NormalizedQuery]
let pages: [String : Page]
}
let batchComplete: String
let query: Query
private enum CodingKeys: String, CodingKey {
case batchComplete = "batchcomplete"
case query
}
}
let responseString = """
{
"batchcomplete" : "",
"query" : {
"normalized" : [
{
"from" : "tokyo",
"to" : "Tokyo"
}
],
"pages" : {
"30057" : {
"pageid" : 30057,
"ns" : 0,
"title" : "Tokyo",
"thumbnail" : {
"source" : "https://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Skyscrapers_of_Shinjuku_2009_January.jpg/50px-Skyscrapers_of_Shinjuku_2009_January.jpg",
"width" : 50,
"height" : 27
},
"pageimage" : "Skyscrapers_of_Shinjuku_2009_January.jpg"
}
}
}
}
"""
let responseData = responseString.data(using: .utf8)!
let response = try! JSONDecoder().decode(Response.self, from: responseData)
print(response)
// Response(batchComplete: "", query: __lldb_expr_18.Response.Query(normalized: [__lldb_expr_18.Response.Query.NormalizedQuery(from: "tokyo", to: "Tokyo")], pages: ["30057": __lldb_expr_18.Response.Query.Page(id: 30057, ns: 0, title: "Tokyo", thumbnail: __lldb_expr_18.Response.Query.Page.Thumbnail(source: https://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Skyscrapers_of_Shinjuku_2009_January.jpg/50px-Skyscrapers_of_Shinjuku_2009_January.jpg, width: 50, height: 27), pageImage: "Skyscrapers_of_Shinjuku_2009_January.jpg")]))