Accessing Nested Dictionaries in JSON with Swift

Question

I want to parse the following JSON in order to get the ID of a random article from Wikipedia's API and use it in Swift:

{
"batchcomplete": "",
"continue": {
    "rncontinue": "0.067678657404|0.067678667039|13394072|0",
    "continue": "-||"
},
"query": {
    "random": [
        {
            "id": 34538560,
            "ns": 3,
            "title": "User talk:59.188.42.121"
        }
    ]
}
}

I want to be able to access the "id" and "title" values from it, and I currently have the following to access "query":

let url = URL(string: "https://en.wikipedia.org/w/api.php?action=query&list=random&rnlimit=1&format=json")
    URLSession.shared.dataTask(with: url!) { (data, response, err) in
        guard let data = data else { return }
        if err != nil {
            print(err!)
        } else {
            do {
                let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? NSDictionary
                if let result = json! as? [String: AnyObject] {
                    if let result = result["query"]! as? [String: AnyObject] {
                        print(result)
                    }
                }
            } catch {
                print("Error")
            }
        }
    }.resume()

Right now, type-casting my way down is not something I'm proud of doing, and it gets very confusing very fast. I've also tried type-casting once by doing something like the following, to no avail:

[String: [String: [String:AnyObject]]]

Is there a better way to access these values? Any help would be greatly appreciated!

Code Different · Accepted Answer · 2018-12-09 03:30:28Z

If you are using Swift 4, there's Codable. Using Codable involves defining custom structs / classes for the JSON but apps like quicktype.io can make that a piece of cake: you just paste the JSON and it generates the structs for you.

First, the struct to hold the response from Wikipedia:

struct Response: Codable {
    struct Query: Codable {
        let random: [Random]
    }

    struct Random: Codable {
        let id, ns: Int
        let title: String
    }

    struct Continue: Codable {
        let rncontinue, continueContinue: String

        enum CodingKeys: String, CodingKey {
            case rncontinue
            case continueContinue = "continue"
        }
    }

    let batchcomplete: String
    let `continue`: Continue
    let query: Query

    enum CodingKeys: String, CodingKey {
        case batchcomplete, `continue`, query
    }
}

And decoding the JSON:

let url = URL(string: "https://en.wikipedia.org/w/api.php?action=query&list=random&rnlimit=1&format=json")
URLSession.shared.dataTask(with: url!) { (data, response, err) in
    guard let data = data else { return }
    guard err == nil else { print(err!); return }

    do {
        let response = try JSONDecoder().decode(Response.self, from: data)
        if let firstArticle = response.query.random.first {
            print(firstArticle)
        } else {
            print("No Article")
        }
    } catch {
        print(error)
    }
}.resume()

Collectives™ on Stack Overflow

Accessing Nested Dictionaries in JSON with Swift

1 Answer 1

Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Related