How do I make an HTTP request in Swift?

Question

I read The Programming Language Swift by Apple in iBooks, but cannot figure out how to make an HTTP request (something like cURL) in Swift. Do I need to import Obj-C classes

Answer 1

Swift 4 and above : Data Request using URLSession API

   //create the url with NSURL
   let url = URL(string: "https://jsonplaceholder.typicode.com/todos/1")! //change the url

   //create the session object
   let session = URLSession.shared

   //now create the URLRequest object using the url object
   let request = URLRequest(url: url)

   //create dataTask using the session object to send data to the server
   let task = session.dataTask(with: request as URLRequest, completionHandler: { data, response, error in

       guard error == nil else {
           return
       }

       guard let data = data else {
           return
       }

      do {
         //create json object from data
         if let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? [String: Any] {
            print(json)
         }
      } catch let error {
        print(error.localizedDescription)
      }
   })

   task.resume()

Swift 4 and above, Decodable and Result enum

//APPError enum which shows all possible errors
enum APPError: Error {
    case networkError(Error)
    case dataNotFound
    case jsonParsingError(Error)
    case invalidStatusCode(Int)
}

//Result enum to show success or failure
enum Result {
    case success(T)
    case failure(APPError)
}

//dataRequest which sends request to given URL and convert to Decodable Object
func dataRequest(with url: String, objectType: T.Type, completion: @escaping (Result) -> Void) {

    //create the url with NSURL
    let dataURL = URL(string: url)! //change the url

    //create the session object
    let session = URLSession.shared

    //now create the URLRequest object using the url object
    let request = URLRequest(url: dataURL, cachePolicy: .useProtocolCachePolicy, timeoutInterval: 60)

    //create dataTask using the session object to send data to the server
    let task = session.dataTask(with: request, completionHandler: { data, response, error in

        guard error == nil else {
            completion(Result.failure(AppError.networkError(error!)))
            return
        }

        guard let data = data else {
            completion(Result.failure(APPError.dataNotFound))
            return
        }

        do {
            //create decodable object from data
            let decodedObject = try JSONDecoder().decode(objectType.self, from: data)
            completion(Result.success(decodedObject))
        } catch let error {
            completion(Result.failure(APPError.jsonParsingError(error as! DecodingError)))
        }
    })

    task.resume()
}

example:

//if we want to fetch todo from placeholder API, then we define the ToDo struct and call dataRequest and pass "https://jsonplaceholder.typicode.com/todos/1" string url.

struct ToDo: Decodable {
    let id: Int
    let userId: Int
    let title: String
    let completed: Bool

}

dataRequest(with: "https://jsonplaceholder.typicode.com/todos/1", objectType: ToDo.self) { (result: Result) in
    switch result {
    case .success(let object):
        print(object)
    case .failure(let error):
        print(error)
    }
}

//this prints the result:

ToDo(id: 1, userId: 1, title: "delectus aut autem", completed: false)