HTTP post request and save response in app - swift

Question

I'm totally new to swift and iOS programming so I'm a little lost on how to do this and even in what files I should be doing this too.
I'm trying to do a http post request to get calendar events and save them in the app to later use and display.
I made a model class with this code.
import UIKit
class Event {
var id: Int
var init_date: String
var end_date: String
var title: String
var description: String
var color_code: String
var all_day: Int
init?(id: Int, init_date: String, end_date: String, title: String, description: String, color_code: String, all_day: Int) {
//Initialization should fail if these are false
if id < 0 || init_date.isEmpty || end_date.isEmpty || title.isEmpty {
return nil
}
//Initialize stored properties
self.id = id
self.init_date = init_date
self.end_date = end_date
self.title = title
self.description = description
self.color_code = color_code
self.all_day = all_day
}
}
But now I don't know what the next step would be. I need this to be downloaded immediately once the app is opened for the first time and not when it's not being opened for the first time. Do I create a new method in the ViewController.swift for the download?
Right now I haven't added anything to the ViewController
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
}
What should I do next?

Answer 1

At this point you need to create a function that handles the POST request you are making.
Once completed, place this function inside your appDelegate main function didFinishLaunchingWithOptions. This is the function that executes on appStart
On a successful function call save the data (presumably json) into a Global Variable or whatever you need for you app.
TIP:
On you class
class Event: Codable {
}
make sure to add Codable like above
Below is an example of what your post request will look like
func myPostRequest(completionHandler: #escaping (Bool?, String?) -> Void){
guard let url = URL(string:"") else { return }
let parameters = ["": ""]
var request: URLRequest = URLRequest(url: url)
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.setValue("", forHTTPHeaderField: "Authorization")
do {
request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard
error == nil
else {
print(error as Any)
return
}
if let httpResponse = response as? HTTPURLResponse {
if (httpResponse.statusCode == 200) {
if let data = data {
let json = try? JSONSerialization.jsonObject(with: data, options: []) as? [[String: Any]]
//print("^^^^^^^^^^^^^^",json)
for x in json ?? [] {
//here is where you will parse your data from the post request
}
completionHandler(true, nil)
return
}
} else {
completionHandler(false, "No Response From Server")
print("Failure response: STATUS CODE != 200")
}
} else {
completionHandler(false, "Database Connection Error")
print("Error \(error!)")
}
}
task.resume()
} catch let error {
completionHandler(false, "failure")
print("POSTERROR: \(error.localizedDescription)")
}
}

Answer 2

I use Alamofire, you can add it to your project via:
Pods
Swift Package Manager
When you add the framework you can use it:
import Alamofire
Then you need to make your class with the protocol Codable to pass the data to your class.
class Event: Codable { }
Then you need to call the url and store the response in a variable:
override func viewDidAppear(_ animated: Bool) {
AF.request("your API rest url").responseData { (resData) in
guard let data = resData.data else { return }//Check if the data is valid
do {
let decoder = JSONDecoder()//Initialize a Json decoder variable
let decodedData = try decoder.decode(Event.self, from: data)//Decode the response data to your decodable class
//Print the values
print(decodedData.headers)
print(decodedData.id)
print(decodedData.init_date)
print(decodedData.end_date)
} catch {
print(error.localizedDescription)
}
}
}