Frozennode\Administrator\Fields\File::build PHP Method

    public function build()
    {
        parent::build();
        //set the upload url depending on the type of config this is
        $url = $this->validator->getUrlInstance();
        $route = $this->config->getType() === 'settings' ? 'admin_settings_file_upload' : 'admin_file_upload';
        //set the upload url to the proper route
        $this->suppliedOptions['upload_url'] = $url->route($route, array($this->config->getOption('name'), $this->suppliedOptions['field_name']));
    }