Swift GET request with parameters

Question

I'm very new to swift, so I will probably have a lot of faults in my code but what I'm trying to achieve is send a GET request to a localhost server with paramters. More so I'm trying to achieve it given my function take two parameters baseURL:string,params:NSDictionary. I am not sure how to combine those two into the actual URLRequest ? Here is what I have tried so far

    func sendRequest(url:String,params:NSDictionary){        let urls: NSURL! = NSURL(string:url)        var request = NSMutableURLRequest(URL:urls)        request.HTTPMethod = "GET"        var data:NSData! =  NSKeyedArchiver.archivedDataWithRootObject(params)        request.HTTPBody = data        println(request)        var session = NSURLSession.sharedSession()        var task = session.dataTaskWithRequest(request, completionHandler:loadedData)        task.resume()      }  }  func loadedData(data:NSData!,response:NSURLResponse!,err:NSError!){     if(err != nil){         println(err?.description)     }else{         var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary         println(jsonResult)      }  } 

Answer 1

When building a GET request, there is no body to the request, but rather everything goes on the URL. To build a URL (and properly percent escaping it), you can also use URLComponents.

var url = URLComponents(string: "https://www.google.com/search/")!  url.queryItems = [     URLQueryItem(name: "q", value: "War & Peace") ] 

The only trick is that most web services need + character percent escaped (because they'll interpret that as a space character as dictated by the application/x-www-form-urlencoded specification). But URLComponents will not percent escape it. Apple contends that + is a valid character in a query and therefore shouldn't be escaped. Technically, they are correct, that it is allowed in a query of a URI, but it has a special meaning in application/x-www-form-urlencoded requests and really should not be passed unescaped.

Apple acknowledges that we have to percent escaping the + characters, but advises that we do it manually:

var url = URLComponents(string: "https://www.wolframalpha.com/input/")!  url.queryItems = [     URLQueryItem(name: "i", value: "1+2") ]  url.percentEncodedQuery = url.percentEncodedQuery?.replacingOccurrences(of: "+", with: "%2B") 

This is an inelegant work-around, but it works, and is what Apple advises if your queries may include a + character and you have a server that interprets them as spaces.

So, combining that with your sendRequest routine, you end up with something like:

func sendRequest(_ url: String, parameters: [String: String], completion: @escaping ([String: Any]?, Error?) -> Void) {     var components = URLComponents(string: url)!     components.queryItems = parameters.map { (key, value) in          URLQueryItem(name: key, value: value)      }     components.percentEncodedQuery = components.percentEncodedQuery?.replacingOccurrences(of: "+", with: "%2B")     let request = URLRequest(url: components.url!)          let task = URLSession.shared.dataTask(with: request) { data, response, error in         guard             let data = data,                              // is there data             let response = response as? HTTPURLResponse,  // is there HTTP response             200 ..< 300 ~= response.statusCode,           // is statusCode 2XX             error == nil                                  // was there no error         else {             completion(nil, error)             return         }                  let responseObject = (try? JSONSerialization.jsonObject(with: data)) as? [String: Any]         completion(responseObject, nil)     }     task.resume() } 

And you'd call it like:

sendRequest("someurl", parameters: ["foo": "bar"]) { responseObject, error in     guard let responseObject = responseObject, error == nil else {         print(error ?? "Unknown error")         return     }      // use `responseObject` here } 

Personally, I'd use JSONDecoder nowadays and return a custom struct rather than a dictionary, but that's not really relevant here. Hopefully this illustrates the basic idea of how to percent encode the parameters into the URL of a GET request.

---

See previous revision of this answer for Swift 2 and manual percent escaping renditions.

Answer 2

Use NSURLComponents to build your NSURL like this

var urlComponents = NSURLComponents(string: "https://www.google.de/maps/")!  urlComponents.queryItems = [   NSURLQueryItem(name: "q", value: String(51.500833)+","+String(-0.141944)),   NSURLQueryItem(name: "z", value: String(6)) ] urlComponents.URL // returns https://www.google.de/maps/?q=51.500833,-0.141944&z=6 

font: https://www.ralfebert.de/snippets/ios/encoding-nsurl-get-parameters/