upload doc on dropbox how to get url

how to get URL uploaded doc on drop box. and how to store this URL our data base. this is the code   
def passport_upload 
        app_key = ENV['APP_DROPBOX_APP_KEY_DEVELOPMENT'] 
        app_secret = ENV['APP_DROPBOX_APP_SECRET_DEVELOPMENT']  
        flow = DropboxOAuth2FlowNoRedirect.new(app_key, app_secret)
        authorize_url = flow.start()
        client=DropboxClient.new(ENV['APP_DROPBOX_ACCESS_TOKEN_DEVELOPMENT'])
        file = open(params[:doc])
        file_name = params[:doc].original_filename 
        response = client.put_file(file_name, file)
  end   

this is the code how to find the url of uploded doc.