code: public function setZipCode( $zipCode )
      {
          $zipCode = preg_replace( '/\D/', '', $zipCode );
  
          if (empty( $zipCode )) {
              throw new InvalidArgumentException( 'ZipCode is empty!' );
          }
  
          $this->zipCode = $zipCode;
  
          return $this;
      }
docs: @param  string $zipCode
  
  @return $this