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 · 2018-02-20T17:40:00.750

165

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 else {                           // was there no error, otherwise ...
                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.

edited Feb 20 '18 at 17:40

answered Dec 31 '14 at 17:57

Rob

371,891
67
713
902

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? – MrSSS16 Jan 01 '15 at 00:26
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`. – Rob Jan 01 '15 at 10:02
This looks so simple, what are the advantages of using something like https://github.com/xyyc/SwiftSocket/ instead of this? I'm sorry I'm new to all this. – jigzat Mar 01 '15 at 18:21
That might not be the right comparison, because that's a sockets library and this is HTTP. Closer is something like [Alamofire](https://github.com/Alamofire/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. – Rob Mar 01 '15 at 19:34
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]` – Isuru Mar 18 '15 at 12:54
It doesn't make much sense to me to be using JSON with `GET` request. If you're sending information to a server, that's `POST`, not `GET`. And you'd specify a different `Content-Type` header. And you don't need any of this percent-encoding stuff. Bottom line, a lot of the execution details are different. – Rob Mar 18 '15 at 13:01
@Rob I see. Thank you. – Isuru Mar 18 '15 at 13:05
Rob . chance you can update the extension method to swfit 2? – Roi Mulia Sep 18 '15 at 18:03
Great answer. I think you can use `NSCharacterSet.URLQueryAllowedCharacterSet()` instead of manually creating the allowed characters. – Eddie Sullivan Jun 13 '16 at 10:51
@EddieSullivan - Not quite. If you do that, you have to make a mutable copy and then remove a few characters, notably `&` and `+`, which `URLQueryAllowedCharacterSet` will allow to pass unescaped. See http://stackoverflow.com/a/35912606/1271826. – Rob Jun 13 '16 at 14:02
@Rob this is a great answer. Could you update it for Swift 3 please? – matt.writes.code Oct 12 '16 at 20:17
Updated for Swift 3. – Rob Oct 12 '16 at 20:19
Just as a note, the dictionary category breaks if the dictionary contains non-string values such as Int data types. – RonLugge Feb 14 '17 at 19:03
Agreed, I was trying to keep it simple, and you might have rendition that handles a broader array of values. For example, [this rendition](http://stackoverflow.com/a/25154803/1271826) renders dates, coordinates, booleans, strings, numeric values, etc. – Rob Feb 14 '17 at 19:37
@Rob this is brilliant - thank you! Everything makes sense except (200 ..< 300) ~= response.statusCode. What does that do please? And what is that operator called - I searched but couldn't find it in Swift. Apologies if that's a really obvious question! – ADB Jul 31 '19 at 11:42
It is the [pattern-matching operator](https://developer.apple.com/documentation/swift/1539154). In this case, it effectively says “does the range of 200 up to (and not including) 300 contain the value `statusCode`.” – Rob Jul 31 '19 at 14:21
Thanks @Rob - that's a great tip! – ADB Jul 31 '19 at 20:18

Ben-Hur Batista · Answer 2 · 2016-09-26T19:27:10.060

94

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/

edited Sep 26 '16 at 19:27

answered Dec 07 '15 at 13:46

Ben-Hur Batista

1,049
7
10

5

In spite of Rob's impressive answer, yours is simpler and works. – Jan ATAC Mar 08 '16 at 13:35
3

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. – John Rogers Jun 01 '16 at 04:10

score 5 · Answer 3 · answered Mar 29 '17 at 16:41

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

Danut Pralea · Answer 4 · 2016-12-23T14:00:59.733

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)")
}

your response doesn't answer OPs question – Ilias Karim Apr 19 '20 at 20:09 — Ilias Karim, Apr 19 '20 at 20:09

score 0 · Answer 5 · answered Jun 12 '17 at 00:41

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

score -1 · Answer 6 · answered Nov 16 '16 at 02:05

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)!
    }

}

score -3 · Answer 7 · answered Jul 22 '16 at 15:10

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);

Swift GET request with parameters

7 Answers7

Linked

Related