Making network requests in iOS with URLSession.

Contents.swift

// Create a playground called NetworkingPlayground, e.g.
// ./NetworkingPlayground.playground/Contents.swift

import UIKit

/*
 {
   "id": 1,
   "title": "Vinyl gloves",
   "merchant": "Shoppers Drug Mart",
   "amount": 20,
   "date": "2020-11-01T00:00:00.000Z",
   "categoryId": 1
 }
 */
struct Expense : Codable {
    var id: Int
    var title: String
    var merchant: String
    var date: String
    var categoryId: Int
    
    // When keys on the backend don't map to keys on the front-end
    // enum CodingKeys : String, CodingKey { case firstName = "first_name" }
}

struct Expenses : Codable {
    var data: [Expense]
}

let session = URLSession.shared

let url = URL(string: "https://aqueous-everglades-71468.herokuapp.com/expenses")!

let task = session.dataTask(with: url) { data, response, error  in
    if error != nil || data == nil {
        print("There was an error")
        return
    }
    
    guard let response = response as? HTTPURLResponse, (200...299).contains(response.statusCode) else {
        print("Server error")
        return
    }
    
    do {
        let expenses = try JSONDecoder().decode(Expenses.self, from: data!)
        for expense in expenses.data {
            print(expense.title)
        }
    } catch let jsonError {
        print("There was an error! \(jsonError)")
    }
}


task.resume()


// Helpful resources:
//    Making network requests with URLSession: https://learnappmaking.com/urlsession-swift-networking-how-to
//    How to use Codable: https://learnappmaking.com/codable-json-swift-how-to
//    Looping over a Codable: https://developer.apple.com/forums/thread/94317