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)

    }

}

Rob · Accepted Answer · 2023-12-08 00:01:23Z

207

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 components = URLComponents(string: "https://www.google.com/search/")!

components.queryItems = [
    URLQueryItem(name: "q", value: "War & Peace")
]

guard let url = components.url else {
    throw URLError(.badURL)
}

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.

When I presented this issue to Apple support, they advised to manually percent escaping the + characters:

components.percentEncodedQuery = components.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.

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

enum WebServiceError: Error {
    case invalidResponse(Data, URLResponse)
    case statusCode(Int, Data)
}

func object<T: Decodable>(from baseUrl: URL, parameters: [String: String]? = nil) async throws -> T {
    guard var components = URLComponents(url: baseUrl, resolvingAgainstBaseURL: false) else {
        throw URLError(.badURL)
    }

    components.queryItems = parameters?.map { (key, value) in
        URLQueryItem(name: key, value: value)
    }
    components.percentEncodedQuery = components.percentEncodedQuery?.replacingOccurrences(of: "+", with: "%2B")

    guard let url = components.url else {
        throw URLError(.badURL)
    }

    let (data, response) = try await URLSession.shared.data(from: url)

    guard let statusCode = (response as? HTTPURLResponse)?.statusCode else {  // is there HTTP response
        throw WebServiceError.invalidResponse(data, response)
    }

    guard 200 ..< 300 ~= statusCode else {                                    // is statusCode 2XX
        throw WebServiceError.statusCode(statusCode, data)
    }

    return try JSONDecoder().decode(T.self, from: data)
}

And you'd call it like:

do {
    let foo: Foo = try await object(from: baseUrl)
    // do something with `foo` here
} catch WebServiceError.statusCode(404, _) {        // if you want, you can catch individual status codes here
    // handle not found error here
} catch {
    // handle other errors here
}

Clearly, there are lots of permutations on the idea, but hopefully this illustrates the basic idea of how to percent encode the parameters into the URL of a GET request.

See previous revisions of this answer for Swift 2, manual percent escaping renditions, and non-Swift concurrency renditions of the above.

edited Dec 8, 2023 at 0:01

answered Dec 31, 2014 at 17:57

Rob

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16 Comments

MrSSS16 Over a year ago

Thanks for the fantastic answer. I just have one question,I am still a bit confused as to what the extension string is doing to the values ? Also when would I need to use HttpBody then?

Rob Over a year ago

The string extension is percent escaping the values per RFC 3986. There are certain characters that have special meanings in URLs (e.g. & separates one parameter from the next, so if & occurs in value, you cannot let it go by unescaped). Regarding HTTPBody, you should not use it in GET request; It is used in POST but not GET.

jigzat Over a year ago

This looks so simple, what are the advantages of using something like github.com/xyyc/SwiftSocket instead of this? I'm sorry I'm new to all this.

Rob Over a year ago

That might not be the right comparison, because that's a sockets library and this is HTTP. Closer is something like Alamofire, but that is (a) more flexible (can handle JSON requests, x-www-form-urlencoded requests, multipart, etc.); (b) more functional (e.g. handles authentication challenges); and (c) gets you out of the weeds of HTTP programming. If anything, my answer above is intended as a cautionary tale of the risks of just creating your own NSMutableURLRequest, pointing out that there's more to it than the OP suggests.

Isuru Over a year ago

This is a beautiful solution. Thanks @Rob. Btw is there any difference in supplying parameters like this NSJSONSerialization.dataWithJSONObject(parameters, options: nil, error: nil)? parameters being an array of dictionaries [String: String]

|

Ben-Hur Batista · Accepted Answer · 2022-12-12 13:08:24Z

104

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

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

edited Dec 12, 2022 at 13:08

answered Dec 7, 2015 at 13:46

Ben-Hur Batista

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2 Comments

Jan ATAC Over a year ago

In spite of Rob's impressive answer, yours is simpler and works.

John Rogers Over a year ago

This should be the accepted answer. It is recommended to use NSURLComponents along with query items to construct URLs. Much safer and less prone to error.

anoop4real · Accepted Answer · 2017-03-29 16:41:29Z

I am using this, try it in playground. Define the base urls as Struct in Constants

struct Constants {

    struct APIDetails {
        static let APIScheme = "https"
        static let APIHost = "restcountries.eu"
        static let APIPath = "/rest/v1/alpha/"
    }
}

private func createURLFromParameters(parameters: [String:Any], pathparam: String?) -> URL {

    var components = URLComponents()
    components.scheme = Constants.APIDetails.APIScheme
    components.host   = Constants.APIDetails.APIHost
    components.path   = Constants.APIDetails.APIPath
    if let paramPath = pathparam {
        components.path = Constants.APIDetails.APIPath + "\(paramPath)"
    }
    if !parameters.isEmpty {
        components.queryItems = [URLQueryItem]()
        for (key, value) in parameters {
            let queryItem = URLQueryItem(name: key, value: "\(value)")
            components.queryItems!.append(queryItem)
        }
    }

    return components.url!
}

let url = createURLFromParameters(parameters: ["fullText" : "true"], pathparam: "IN")

//Result url= https://restcountries.eu/rest/v1/alpha/IN?fullText=true

Dani Pralea · Accepted Answer · 2016-12-23 14:00:59Z

1

Swift 3:

extension URL {
    func getQueryItemValueForKey(key: String) -> String? {
        guard let components = NSURLComponents(url: self, resolvingAgainstBaseURL: false) else {
              return nil
        }

        guard let queryItems = components.queryItems else { return nil }
     return queryItems.filter {
                 $0.name.lowercased() == key.lowercased()
                 }.first?.value
    }
}

I used it to get the image name for UIImagePickerController in func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]):

var originalFilename = ""
if let url = info[UIImagePickerControllerReferenceURL] as? URL, let imageIdentifier = url.getQueryItemValueForKey(key: "id") {
    originalFilename = imageIdentifier + ".png"
    print("file name : \(originalFilename)")
}

edited Dec 23, 2016 at 14:00

answered Dec 23, 2016 at 13:47

Dani Pralea

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1 Comment

Ilias Karim Over a year ago

your response doesn't answer OPs question

Reza Shirazian · Accepted Answer · 2017-06-12 00:41:20Z

0

You can extend your Dictionary to only provide stringFromHttpParameter if both key and value conform to CustomStringConvertable like this

extension Dictionary where Key : CustomStringConvertible, Value : CustomStringConvertible {
  func stringFromHttpParameters() -> String {
    var parametersString = ""
    for (key, value) in self {
      parametersString += key.description + "=" + value.description + "&"
    }
    return parametersString
  }
}

this is much cleaner and prevents accidental calls to stringFromHttpParameters on dictionaries that have no business calling that method

answered Jun 12, 2017 at 0:41

Reza Shirazian

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Comments

Chris · Accepted Answer · 2023-11-22 21:09:04Z

func relationsApi(_ search: String) {
      let url = URL(string: getApiUrl)!
      
      let session = URLSession.shared
      let queryItems = [URLQueryItem(name: "search", value: search)]
      var urlComps = URLComponents(string: getApiUrl)!
      urlComps.queryItems = queryItems
      let result = urlComps.url!
      print(result)
      
      var request = URLRequest(url: result)
      
      request.setValue( "Bearer \(tokenName)", forHTTPHeaderField: "Authorization")
      let task = session.dataTask(with: request) { (data, response, error) in
          if let error = error{
              print (error)
          } else if let data = data {
              do {
                  let decoder = JSONDecoder()
                  let responseDatas = try decoder.decode(RelationsAPIModel.self, from: data)
                  //  print(responseDatas)
                  DispatchQueue.main.async {
                      
                      self.namesArr = responseDatas.data.relation
                      //     self.subname = responseDatas.data.relation[Re]
                      self.relationTableView.reloadData()
                  }
              } catch {
                  print(error)
              }
          } else {
              print("something went wrong")
          }
      }
      task.resume()
    }
}

etayluz · Accepted Answer · 2016-11-16 02:05:21Z

This extension that @Rob suggested works for Swift 3.0.1

I wasn't able to compile the version he included in his post with Xcode 8.1 (8B62)

extension Dictionary {

    /// Build string representation of HTTP parameter dictionary of keys and objects
    ///
    /// :returns: String representation in the form of key1=value1&key2=value2 where the keys and values are percent escaped

    func stringFromHttpParameters() -> String {

        var parametersString = ""
        for (key, value) in self {
            if let key = key as? String,
               let value = value as? String {
                parametersString = parametersString + key + "=" + value + "&"
            }
        }
        parametersString = parametersString.substring(to: parametersString.index(before: parametersString.endIndex))
        return parametersString.addingPercentEncoding(withAllowedCharacters: .urlHostAllowed)!
    }

}

Fabio Guerra · Accepted Answer · 2016-07-22 15:10:32Z

-4

I use:

let dictionary = ["method":"login_user",
                  "cel":mobile.text!
                  "password":password.text!] as  Dictionary<String,String>

for (key, value) in dictionary {
    data=data+"&"+key+"="+value
    }

request.HTTPBody = data.dataUsingEncoding(NSUTF8StringEncoding);

answered Jul 22, 2016 at 15:10

Fabio Guerra

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