Swift GET request with parameters

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.

Use NSURLComponents to build your NSURLlike 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/

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