iOS Yelp OAuth Token Retrieval with URLRequest returning "client_id or client_secret parameters not found

Question

I am attempting to retrieve an OAuth token to use Yelp's Fusion API from an iOS client using the native URL and URLRequest classes, but it is giving me this error in the "tokenInfo" variable:

client_id or client_secret parameters not found. Make sure to provide 
client_id and client_secret in the body with the 
application/x-www-form-urlencoded content-type

Here is my code:

func getToken(){
    var yelpTokenEndpoint = "https://api.yelp.com/oauth2/token"
    var tokenURL = URL(string: yelpTokenEndpoint)

    let requestJSON: [String:String] = ["client_id":"Not showing actual client id", "client_secret":"Not Gonna Show My Actual Client Secret either","grant_type":"client_credentials"]
    let requestData = try? JSONSerialization.data(withJSONObject: requestJSON)
    print(try? JSONSerialization.jsonObject(with: requestData!, options: []))
    var tokenURLRequest = URLRequest(url: tokenURL!)

    tokenURLRequest.httpMethod = "POST"
    tokenURLRequest.httpBody = requestData!
    tokenURLRequest.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "content-type")

    let tokenSession = URLSession.shared

    let tokenTask = tokenSession.dataTask(with: tokenURLRequest) { (data, response, error) in
        if error != nil {
            print("error getting your access token")
            print(error!.localizedDescription)
        }

        if let data = data{
            do{
                if let tokenInfo = try JSONSerialization.jsonObject(with: data, options: []) as? [String:Any]{
                    let token: String = tokenInfo["access_token"] as! String
                    print(token)
                }
            } catch {
                print("Error converting to JSON")
            }
        }
    }
    tokenTask.resume()
}

And yes, I am certain that I put the right client credentials in. Any help would be much appreciated, thanks!

Answer 1

Try this ....

let clientId = "client_id"
let clientSecret = "client_secret"
let tokenURL = "https://api.yelp.com/oauth2/token"
let grantType = "client_credentials"


let url = NSURL(string: tokenURL as String );

let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())

let request = NSMutableURLRequest(URL: NSURL(string: tokenURL)!)
request.HTTPMethod = "POST";
request.HTTPShouldHandleCookies = true
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")


let postString = "client_id=" + clientId + "&client_secret=" + clientSecret + "&grant_type=" + grantType
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)

let task: NSURLSessionDataTask = session.dataTaskWithRequest(request) { (data, response, error) -> Void in
    if let data = data {
        let response = NSString(data: data, encoding: NSUTF8StringEncoding)
        print(response)
    }
}
task.resume()