def create
    user_password = params[:password]
    user_email = params[:email]
    user = user_email.present? && User.find_by(email: user_email)

    if user.valid_password?(user_password)
        sign_in user, store: false
        user.generate_authentication_token!
        user.save
        render json: user, status: 200, location: [:api, user]
    else
        render json: { errors: "Invalid Email or password", status: 422 }
    end
end

func postrequest() {
    let string = "http://localhost:3000/api/sessions"
    let url = NSURL(string: string)
    let session = NSURLSession.sharedSession()
    let request = NSMutableURLRequest(URL: url!)
    let params = ["email": "myEmail@yahoo.fr", "password": "myPassword"]
    request.HTTPMethod = "POST"
    do {
         request.HTTPBody = try NSJSONSerialization.dataWithJSONObject(params, options: NSJSONWritingOptions())

    }
    catch {

    }
    let tache = session.dataTaskWithRequest(request) { (data, response, error) -> Void in
        //
        if let antwort = response as? NSHTTPURLResponse {
            let code = antwort.statusCode
            print(code)
            do {
                let json = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers)
                print(json)
            }
            catch {

            }
        }
    }
    tache.resume()
}

Rails.application.routes.draw do
 devise_for :users
  namespace :api, defaults: {format: :json} do
  scope module: :v1, constraints: ApiConstraints.new(version: 1, default: true) do
  resources :users, :only => [:show, :create, :update, :destroy] do
    resources :prodcuts, :only => [:create, :update, :destroy]
  end
  resources :sessions, :only => [:create, :destroy]
  resources :products, :only => [:show, :index]
    end
  end
end

api_sessions POST   /api/sessions(.:format)
api/v1/sessions#create {:format=>:son}