HTTP Request in Swift with POST method

I'm trying to run a HTTP Request in Swift, to POST 2 parameters to a URL.

Example:

Link: www.thisismylink.com/postName.php

Params:

id = 13
name = Jack

What is the simplest way to do that?

I don't even want to read the response. I just want to send that to perform changes on my database through a PHP file.

The key is that you want to:

• set the httpMethod to POST;
• optionally, set the Content-Type header, to specify how the request body was encoded, in case server might accept different types of requests;
• optionally, set the Accept header, to request how the response body should be encoded, in case the server might generate different types of responses; and
• set the httpBody to be properly encoded for the specific Content-Type; e.g. if application/x-www-form-urlencoded request, we need to percent-encode the body of the request.

E.g., in Swift 3 and later you can:

let url = URL(string: "https://httpbin.org/post")!
var request = URLRequest(url: url)
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
request.setValue("application/json", forHTTPHeaderField: "Accept")
request.httpMethod = "POST"
let parameters: [String: Any] = [
    "id": 13,
    "name": "Jack & Jill"
]
request.httpBody = parameters.percentEncoded()

let task = URLSession.shared.dataTask(with: request) { data, response, error in
    guard 
        let data = data, 
        let response = response as? HTTPURLResponse, 
        error == nil 
    else {                                                               // check for fundamental networking error
        print("error", error ?? URLError(.badServerResponse))
        return
    }
    
    guard (200 ... 299) ~= response.statusCode else {                    // check for http errors
        print("statusCode should be 2xx, but is \(response.statusCode)")
        print("response = \(response)")
        return
    }
    
    // do whatever you want with the `data`, e.g.:
    
    do {
        let responseObject = try JSONDecoder().decode(ResponseObject<Foo>.self, from: data)
        print(responseObject)
    } catch {
        print(error) // parsing error
        
        if let responseString = String(data: data, encoding: .utf8) {
            print("responseString = \(responseString)")
        } else {
            print("unable to parse response as string")
        }
    }
}

task.resume()

Where the following extensions facilitate the percent-encoding request body, converting a Swift Dictionary to a application/x-www-form-urlencoded formatted Data:

extension Dictionary {
    func percentEncoded() -> Data? {
        map { key, value in
            let escapedKey = "\(key)".addingPercentEncoding(withAllowedCharacters: .urlQueryValueAllowed) ?? ""
            let escapedValue = "\(value)".addingPercentEncoding(withAllowedCharacters: .urlQueryValueAllowed) ?? ""
            return escapedKey + "=" + escapedValue
        }
        .joined(separator: "&")
        .data(using: .utf8)
    }
}

extension CharacterSet { 
    static let urlQueryValueAllowed: CharacterSet = {
        let generalDelimitersToEncode = ":#[]@" // does not include "?" or "/" due to RFC 3986 - Section 3.4
        let subDelimitersToEncode = "!$&'()*+,;="
        
        var allowed: CharacterSet = .urlQueryAllowed
        allowed.remove(charactersIn: "\(generalDelimitersToEncode)\(subDelimitersToEncode)")
        return allowed
    }()
}

And the following Decodable model objects facilitate the parsing of the application/json response using JSONDecoder:

// sample Decodable objects for https://httpbin.org

struct ResponseObject<T: Decodable>: Decodable {
    let form: T    // often the top level key is `data`, but in the case of https://httpbin.org, it echos the submission under the key `form`
}

struct Foo: Decodable {
    let id: String
    let name: String
}

This checks for both fundamental networking errors as well as high-level HTTP errors. This also properly percent escapes the parameters of the query.

Note, I used a name of Jack & Jill, to illustrate the proper x-www-form-urlencoded result of name=Jack%20%26%20Jill, which is “percent encoded” (i.e. the space is replaced with %20 and the & in the value is replaced with %26).

---

See previous revision of this answer for Swift 2 rendition.

Swift 4 and above

func postRequest() {
  
  // declare the parameter as a dictionary that contains string as key and value combination. considering inputs are valid
  
  let parameters: [String: Any] = ["id": 13, "name": "jack"]
  
  // create the url with URL
  let url = URL(string: "www.thisismylink.com/postName.php")! // change server url accordingly
  
  // create the session object
  let session = URLSession.shared
  
  // now create the URLRequest object using the url object
  var request = URLRequest(url: url)
  request.httpMethod = "POST" //set http method as POST
  
  // add headers for the request
  request.addValue("application/json", forHTTPHeaderField: "Content-Type") // change as per server requirements
  request.addValue("application/json", forHTTPHeaderField: "Accept")
  
  do {
    // convert parameters to Data and assign dictionary to httpBody of request
    request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
  } catch let error {
    print(error.localizedDescription)
    return
  }
  
  // create dataTask using the session object to send data to the server
  let task = session.dataTask(with: request) { data, response, error in
    
    if let error = error {
      print("Post Request Error: \(error.localizedDescription)")
      return
    }
    
    // ensure there is valid response code returned from this HTTP response
    guard let httpResponse = response as? HTTPURLResponse,
          (200...299).contains(httpResponse.statusCode)
    else {
      print("Invalid Response received from the server")
      return
    }
    
    // ensure there is data returned
    guard let responseData = data else {
      print("nil Data received from the server")
      return
    }
    
    do {
      // create json object from data or use JSONDecoder to convert to Model stuct
      if let jsonResponse = try JSONSerialization.jsonObject(with: responseData, options: .mutableContainers) as? [String: Any] {
        print(jsonResponse)
        // handle json response
      } else {
        print("data maybe corrupted or in wrong format")
        throw URLError(.badServerResponse)
      }
    } catch let error {
      print(error.localizedDescription)
    }
  }
  // perform the task
  task.resume()
}

For anyone looking for a clean way to encode a POST request in Swift 5.

You don’t need to deal with manually adding percent encoding. Use URLComponents to create a GET request URL. Then use query property of that URL to get properly percent escaped query string.

let url = URL(string: "https://example.com")!
var components = URLComponents(url: url, resolvingAgainstBaseURL: false)!

components.queryItems = [
    URLQueryItem(name: "key1", value: "NeedToEscape=And&"),
    URLQueryItem(name: "key2", value: "vålüé")
]

let query = components.url!.query

The query will be a properly escaped string:

> key1=NeedToEscape%3DAnd%26&key2=v%C3%A5l%C3%BC%C3%A9

Now you can create a request and use the query as HTTPBody:

var request = URLRequest(url: url)
request.httpMethod = "POST"
request.httpBody = Data(query.utf8)

Now you can send the request.

Heres the method I used in my logging library: https://github.com/goktugyil/QorumLogs

This method fills html forms inside Google Forms.

    var url = NSURL(string: urlstring)
    
    var request = NSMutableURLRequest(URL: url!)
    request.HTTPMethod = "POST"
    request.setValue("application/x-www-form-urlencoded; charset=utf-8", forHTTPHeaderField: "Content-Type")
    request.HTTPBody = postData.dataUsingEncoding(NSUTF8StringEncoding)
    var connection = NSURLConnection(request: request, delegate: nil, startImmediately: true)
    

let session = URLSession.shared
        let url = "http://...."
        let request = NSMutableURLRequest(url: NSURL(string: url)! as URL)
        request.httpMethod = "POST"
        request.addValue("application/json", forHTTPHeaderField: "Content-Type")
        var params :[String: Any]?
        params = ["Some_ID" : "111", "REQUEST" : "SOME_API_NAME"]
        do{
            request.httpBody = try JSONSerialization.data(withJSONObject: params, options: JSONSerialization.WritingOptions())
            let task = session.dataTask(with: request as URLRequest as URLRequest, completionHandler: {(data, response, error) in
                if let response = response {
                    let nsHTTPResponse = response as! HTTPURLResponse
                    let statusCode = nsHTTPResponse.statusCode
                    print ("status code = \(statusCode)")
                }
                if let error = error {
                    print ("\(error)")
                }
                if let data = data {
                    do{
                        let jsonResponse = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions())
                        print ("data = \(jsonResponse)")
                    }catch _ {
                        print ("OOps not good JSON formatted response")
                    }
                }
            })
            task.resume()
        }catch _ {
            print ("Oops something happened buddy")
        }

All the answers here use JSON objects. This gave us problems with the $this->input->post() methods of our Codeigniter controllers. The CI_Controller cannot read JSON directly. We used this method to do it WITHOUT JSON

func postRequest() {
    // Create url object
    guard let url = URL(string: yourURL) else {return}

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

    // Create the URLRequest object using the url object
    var request = URLRequest(url: url)

    // Set the request method. Important Do not set any other headers, like Content-Type
    request.httpMethod = "POST" //set http method as POST

    // Set parameters here. Replace with your own.
    let postData = "param1_id=param1_value&param2_id=param2_value".data(using: .utf8)
    request.httpBody = postData

    // Create a task using the session object, to run and return completion handler
    let webTask = session.dataTask(with: request, completionHandler: {data, response, error in
    guard error == nil else {
        print(error?.localizedDescription ?? "Response Error")
        return
    }
    guard let serverData = data else {
        print("server data error")
        return
    }
    do {
        if let requestJson = try JSONSerialization.jsonObject(with: serverData, options: .mutableContainers) as? [String: Any]{
            print("Response: \(requestJson)")
        }
    } catch let responseError {
        print("Serialisation in error in creating response body: \(responseError.localizedDescription)")
        let message = String(bytes: serverData, encoding: .ascii)
        print(message as Any)
    }

    // Run the task
    webTask.resume()
}

Now your CI_Controller will be able to get param1 and param2 using $this->input->post('param1') and $this->input->post('param2')

@IBAction func btn_LogIn(sender: AnyObject) {
    
    let request = NSMutableURLRequest(URL: NSURL(string: "http://demo.hackerkernel.com/ios_api/login.php")!)
    request.HTTPMethod = "POST"
    let postString = "email: [email protected] & password: testtest"
    request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request){data, response, error in
        guard error == nil && data != nil else{
            print("error")
            return
        }
        if let httpStatus = response as? NSHTTPURLResponse where httpStatus.statusCode != 200{
            print("statusCode should be 200, but is \(httpStatus.statusCode)")
            print("response = \(response)")
        }
        let responseString = String(data: data!, encoding: NSUTF8StringEncoding)
        print("responseString = \(responseString)")
    }
    task.resume()
}