public function filter( )
    {
        if ( preg_match( $this->getPrefixPattern(), $this->request->uri, $tokenMatches ) )
        {
            $this->versionToken = isset( $tokenMatches['version'] ) ? $tokenMatches['version'] : '';
            $this->apiProviderToken = isset( $tokenMatches['provider'] ) ? $tokenMatches['provider'] : '';

            self::$version = $this->parseVersionValue();
            self::$apiProvider = empty( $this->apiProviderToken ) ? null : $this->apiProviderToken;
        }
    }