The right way to parse JSON in Swift utilizing Codable protocol?

Dependencies

To begin with only a few phrases about dependencies. From Swift 4 you don’t want any dependency to parse JSON information, as a result of there are built-in protocols to handle the whole lot. In case you are nonetheless utilizing some form of Third-party it’s best to positively ditch it for the sake of simplicity. By the best way earlier than you add any exterior dependency into your challenge, please assume twice. 🤔

Networking

In case your job is solely to load some form of JSON doc via HTTP from across the net, – shock – you received’t want Alamofire in any respect. You should utilize the built-in URLSession class to make the request, and get again the whole lot that you just’ll want. The Basis networking stack is already a fancy and really helpful stack, don’t make issues much more difficult with further layers.

JSON parsing

Now, after the brief intro, let’s dive in and get some actual pretend JSON information from the JSONPlaceholder net service. I’m going to put the entire thing proper right here, you possibly can choose it, copy and paste right into a Swift playground file.

import Basis
import PlaygroundSupport

PlaygroundPage.present.needsIndefiniteExecution = true

struct Submit: Codable {

    enum CodingKeys: String, CodingKey {
        case id
        case title
        case physique
        case userIdentifier = "userId"
    }

    let id: Int
    let title: String
    let physique: String
    let userIdentifier: Int
}

let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!

URLSession.shared.dataTask(with: url) { information, response, error in
    if let error = error {
        print("Error: (error.localizedDescription)")
        PlaygroundPage.present.finishExecution()
    }
    guard 
        let httpResponse = response as? HTTPURLResponse, 
        httpResponse.statusCode == 200 
    else {
        print("Error: invalid HTTP response code")
        PlaygroundPage.present.finishExecution()
    }
    guard let information = information else {
        print("Error: lacking information")
        PlaygroundPage.present.finishExecution()
    }

    // be at liberty to uncomment this for debugging information
    // print(String(information: information, encoding: .utf8))

    do {
        let decoder = JSONDecoder()
        let posts = strive decoder.decode([Post].self, from: information)

        print(posts.map { $0.title })
        PlaygroundPage.present.finishExecution()
    }
    catch {
        print("Error: (error.localizedDescription)")
        PlaygroundPage.present.finishExecution()
    }
}.resume()

As you possibly can see downloading and parsing JSON from the online is a very easy job. This entire code snippet is round 50 traces of code. After all it’s only a proof of idea, however it works and also you don’t want any dependency. It’s pure Swift and Basis.

NOTE: To save some typing, you too can generate the ultimate objects immediately from the JSON construction with these wonderful Xcode extensions.

The Codable protocol – which is definitely a compound typealias from Encodable & Decodable protocols – makes the method of parsing JSON information in Swift magical. 💫