php command

command.sample.php

<?php
class Data
{
    private $_value;
    private $_error;

    function __construct( $name, $value ){
        $this->_name  = $name;
        $this->_value = $value;
    }

    public function validate_require(){
        if( strlen( $this->_value ) == 0 ){
            $this->_error = "require error";
            return false;
        }
        return true;
    }

    public function validate_maxlength( $max_length ){
        if( strlen( $this->_value ) > $max_length ){
            $this->_error = "length $max_length over";
            return false;
        }
        return true;
    }

    public function print_error(){
        print $this->_error."\n";
    }
}

abstract class Command
{
    abstract function execute();
}

class ValidateRequireCommand extends Command
{
    private $_data;

    function __construct( $data ){
        $this->_data = $data;
    }

    public function execute(){
        if( ! $this->_data->validate_require() ){
            $this->_data->print_error();
            return false;
        }
        return true;
    }
}

class ValidateMaxLengthCommand extends Command
{
    private $_data;
    private $_max_len;

    function __construct( $data, $max_len ){
        $this->_data    = $data;
        $this->_max_len = $max_len;
    }

    public function execute(){
        if(! $this->_data->validate_maxlength( $this->_max_len ) ){
            $this->_data->print_error();
            return false;
        }
        return true;
    }
}

class Invoker
{
    private $commands = array();

    public function add( $command ){
        $this->_commands[] = $command;
    }

    public function clear(){
        $this->_commands = array();
    }

    function invoke(){
        foreach( $this->_commands as $command ){
            if( ! $command->execute() ){
                break;
            }
        }
    }
}

//this instance is not abstract type
$reciever = new Data( "hoge", "" );
$invoker = new Invoker();
$invoker->add( new ValidateRequireCommand( $reciever ) );
$invoker->add( new ValidateMaxLengthCommand( $reciever, 5 ) );
$invoker->invoke();
$invoker->clear();

$reciever = new Data( "hoge", "abcdefg" );
$invoker->add( new ValidateRequireCommand( $reciever ) );
$invoker->add( new ValidateMaxLengthCommand( $reciever, 5 ) );
$invoker->invoke();