系統框圖：
命令分發控制器主要有四個任務：快取
1 命令分發控制器主要有四個任務：快取
可以使用序列化機制，把資料快取而不用每次去讀取文件，加快存取效率。
2.根據前端請求，收集參數產生一個請求(Request)。
3.把請求對應到特定業務邏輯的命令模組(Command)。 4.執行操作並將結果回傳給前端視圖。
業務邏輯層根據傳入的context物件可以取得執行參數，執行完畢後還可以將執行結果透過context物件回傳給上一層。
指令分發控制器的實作：
class Controller{
private function __construct() {}
static function run(){
$instance = new Controller();
$instance->init();
$instance->handleRequest();
}
function init(){
$application
= \base\ApplicationHelper::instance();
$application->system_init();
}
function handleRequest(){
$request = new \controller\Request();
$cmd_r = new \command\CommandResolver();
$cmd = $cmd_r->get_command($request);
$cmd->execute($request);
}
}對於類似PHP這樣的解釋型的語言，要實現undeo/redo機制，必須用到一些緩存機制(session)來保存命令執行的歷史記錄。這裡的session模組主要負責維護一個命令歷史記錄，其實現如下：
namespace base;
require_once('session_registry.php');
class SessionMementoTaker extends SessionRegistry{
const COMMAND_COUNT = 5;
private $persent = 0;
private $cmd_stack = array();
static public function instance(){
return parent::instance();
}
public function push_command(Command $cmd){
$this->cmd_stack = self::instance()->get('cmd_stack');
if(!empty($this->cmd_stack)){
if(count($this->cmd_stack) >self::COMMAND_COUNT){
array_shift($this->cmd_stack);
reset($this->cmd_stack);
}
}
array_push($this->cmd_stack, $cmd);
$this->persent = count($this->cmd_stack) + 1;
self::instance()->set('cmd_stack', $this->cmd_stack);
self::instance()->set('cmd_persent', $this->persent);
}
public function get_undo_command(){
$this->persent = self::instance()->get('cmd_persent');
$this->cmd_stack = self::instance()->get('cmd_stack');
if(!empty($this->cmd_stack) && $this->persent > 0){
$command = $this->cmd_stack[--$this->persent];
self::instance()->set('cmd_persent', $this->persent);
return $command;
}
return null;
}
public function get_redo_command(){
$this->persent = self::instance()->get('cmd_persent');
$this->cmd_stack = self::instance()->get('cmd_stack');
if(!empty($this->cmd_stack) && $this->persent < count($this->cmd_stack)){
$command = $this->cmd_stack[$this->persent++];
self::instance()->set('cmd_persent', $this->persent);
return $command;
}
return null;
}
}command基類實現：
namespace woo\command;
require_once('../memento/state.php');
require_once('../memento/memento.php');
abstract class Command {
protected $state;
final function __construct(){
$this->state = new \woo\memento\State();
}
function execute(\woo\controller\Request $request) {
$this->state->set('request', $request);
$this->do_execute($request);
}
abstract function do_execute(\woo\controller\Request $request);
function do_unexecute(\woo\controller\Request $request) {}
public function get_state(){
return $this->state;
}
public function set_state(State $state){
$this->state = $state;
}
public function get_request(){
if(isset($this->state)){
return $this->state->get('request');
}
return null;
}
public function set_request(\woo\controller\Request $request){
if(isset($this->state)){
return $this->state->set('request', $request);
}
}
public function create_memento(){
\woo\base\SessionMementoTaker::push_command($this);
$mem = new \woo\memento\Memento();
$mem->set_state($this->state);
return $mem;
}
public function set_memento(Memento $mem){
$this->state = $mem->get_state();
}
}保存指令狀態的物件：
class State{
private $values = array();
function __construct(){
}
public function set($key, $value){
$this->values[$key] = $value;
}
public function get($key){
if(isset($this->values[$key]))
{
return $this->values[$key];
}
return null;
}
}最後是要實現的undo-redo，在這裡我把undo/redo也看成是一次普通的命令請求，而不需要在控制器做額外的分發處理。
撤銷指令：
namespace woo\command;
require_once('request.php');
require_once('command.php');
require_once('../base/registry.php');
require_once('../file_manager.php');
require_once('../base/session_memento.php');
class CopyCommand extends Command {
function do_execute(\controller\Request $request) {
$src_path = $request->get_property('src');
$dst_path = $request->get_property('dst');
$this->state->set('src_path', $src_path);
$this->state->set('dst_path', $dst_path);
$this->create_memento();
$file_manager = \base\Registry::file_manager();
$ret = $file_manager->copy($src_path, $dst_path);
$request->add_feedback($ret);
//...
}
}重做指令：
namespace woo\command;
require_once('request.php');
require_once('command.php');
require_once('../base/registry.php');
require_once('../base/session_memento.php');
class UndoCommand extends Command{
public function do_execute(\controller\Request $request){
$command = \base\SessionMementoTaker::get_undo_command();
if(isset($command)){
$old_req = $command->get_request();
$command->do_unexecute($old_req);
$request->set_feedback($old_req->get_feedback());
} else{
$request->add_feedback('undo command not fount');
}
return;
}
}
以上就介紹了重做(redo)和撤銷(undo)的完整實現，包括了方面的內容，希望對PHP教程有興趣的朋友有所幫助。
