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

Dependencies

Initially just some phrases about dependencies. From Swift 4 you do not want any dependency to parse JSON information, as a result of there are built-in protocols to deal with every little thing. In case you are nonetheless utilizing some sort of Third-party you must undoubtedly ditch it for the sake of simplicity. By the way in which earlier than you add any exterior dependency into your challenge, please suppose twice. 🤔

Networking

In case your activity is solely to load some sort of JSON doc by HTTP from across the net, – shock – you will not want Alamofire in any respect. You should use the built-in URLSession class to make the request, and get again every little thing that you will want. The Basis networking stack is already a posh and really helpful stack, do not 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 will place the entire thing proper right here, you may choose it, copy and paste right into a Swift playground file.

import Basis
import PlaygroundSupport

PlaygroundPage.present.needsIndefiniteExecution = true

struct Publish: 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()
    }

    

    do {
        let decoder = JSONDecoder()
        let posts = attempt 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 may see downloading and parsing JSON from the online is a very easy activity. This entire code snippet is round 50 strains of code. In fact it is only a proof of idea, however it works and you do not want any dependency. It is pure Swift and Basis.

To save some typing, you may also generate the ultimate objects instantly from the JSON construction with these superb 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. 💫