How to parse JSON in Swift with dynamic filename using Codable

Question

I am trying to parse the following JSON into a class, but don't know how to approach this particular case.

Here is the api: https://en.wikipedia.org/w/api.php?format=json&action=query&prop=extracts&exintro=&explaintext=&indexpageids&titles=bird

I am trying to get the title and extract, but in order to do so, it requires that I go through the unique pageid. How would I do this using the Codable protocol?

{ 
    "batchcomplete": "", 
    "query": { 
        "normalized": [
           {
               "from": "bird",
               "to": "Bird"
           }
         ],
         "pageids": [
             "3410"
         ],
         "pages": {
            "3410": {
                "pageid": 3410,
                "ns": 0,
                "title": "Bird",
                "extract": "..."
            }
         }
     }
}

vadian · Accepted Answer · 2020-04-15 08:03:03Z

My suggestion is to write a custom initializer:

Decode pages as [String:Page] dictionary and map the inner dictionaries according to the values in pageids

let jsonString = """
{
    "batchcomplete": "",
    "query": {
        "normalized": [
           {
               "from": "bird",
               "to": "Bird"
           }
         ],
         "pageids": [
             "3410"
         ],
         "pages": {
            "3410": {
                "pageid": 3410,
                "ns": 0,
                "title": "Bird",
                "extract": "..."
            }
         }
     }
}
"""

struct Root : Decodable {
    let query : Query
}

struct Query : Decodable {
    let pageids : [String]
    let pages : [Page]

    private enum CodingKeys : String, CodingKey { case pageids, pages }

    init(from decoder : Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        self.pageids = try container.decode([String].self, forKey: .pageids)
        let pagesData = try container.decode([String:Page].self, forKey: .pages)
        self.pages = self.pageids.compactMap{ pagesData[$0] }
    }
}

struct Page : Decodable {
    let pageid, ns : Int
    let title, extract : String
}


let data = Data(jsonString.utf8)

do {
    let result = try JSONDecoder().decode(Root.self, from: data)
    print(result)
} catch {
    print(error)
}

Collectives™ on Stack Overflow

How to parse JSON in Swift with dynamic filename using Codable

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related