轻松掌握php设计模式之访问者模式

  /
   抽象基类
  /
  abstract class Unit
  {
    /
    获取名称
    /
    abstract public function getName();

  }

  /
   Cpu类
  /
  class Cpu extends Unit
  {
    public function getName()
    {
      return 'i am cpu';
    }
  }

  /
   内存类
  /
  class Memory extends Unit
  {
    public function getName()
    {
      return 'i am memory';
    }
  }

  /
   键盘类
  /
  class Keyboard extends Unit
  {
    public function getName()
    {
      return 'i am keyboard';
    }
  }

  /
   计算机类
  /
  class Computer
  {
    protected $_items = [];

    public function add(Unit $unit)
    {
      $this->_items[] = $unit;
    }

    public function print()
    {
      // 循环打印各个组成部分
      foreach ($this->_items as $item) {
        $item->getName();
      }
    }
  }

  /
   抽象基类
  /
  abstract class Unit
  {
    /
     获取名称
    /
    abstract public function getName();

    /
     用来接受访问者对象，回调访问者的visit方法
     非常关键的方法
    /
    public function aept(Visitor $visitor)
    {
      $method = visit . get_class($this);
      if (method_exists($visitor, $method)) {
        $visitor->$method($this);
      }
    }
  }

  /
   Cpu类
  /
  class Cpu extends Unit
  {
    public function getName()
    {
      return 'i am cpu';
    }
  }

  /
   Memory类
  /
  class Memory extends Unit
  {
    public function getName()
    {
      return 'i am memory';
    }
  }

  /
   Keyboard类
  /
  class Keyboard extends Unit
  {
    public function getName()
    {
      return 'i am keyboard';
    }
  }
  
  /
   Keyboard类
  /
  interface Visitor
  {
    public function visitCpu(Cpu $cpu);
    public function visitMemory(Memory $memory);
    public function visitKeyboard(Keyboard $keyboard);
  }

  /
   
  /
  class PrintVisitor implements Visitor
  {
    public function visitCpu(Cpu $cpu)
    {
      echo "hello, " . $cpu->getName() . "\n";
    }

    public function visitMemory(Memory $memory)
    {
      echo "hello, " . $memory->getName() . "\n";
    }

    public function visitKeyboard(Keyboard $keyboard)
    {
      echo "hello, " . $keyboard->getName() . "\n";
    }
  }

  /
   
  /
  class Computer
  {
    protected $_items = [];

    public function add(Unit $unit)
    {
      $this->_items[] = $unit;
    }
    
    /
     调用各个组件的aept方法
    /
    public function aept(Visitor $visitor)
    {
      foreach ($this->_items as $item) {
        $item->aept($visitor);
      }
    }
  }

  $puter = new Computer();
  $puter->add(new Cpu());
  $puter->add(new Memory());
  $puter->add(new Keyboard());

  $printVisitor = new PrintVisitor();
  $puter->print($printVisitor);

  // 以上的代码将打印出  
  hello, i am cpu
  hello, i am memory
  hello, i am keyboard