PHP设计模式之迭代器（Iterator）模式入门与应用详解

class MyIterator implements Iterator
{
   private $var = array();
 
   public function __construct($array)
   {
     if (is_array($array)) {
      $this->var = $array;
     }
   }
 
   public function rewind() {
     echo "倒回第一个元素\n";
    reset($this->var);
   }
 
   public function current() {
    $var = current($this->var);
     echo "当前元素: $var\n";
     return $var;
   }
 
   public function key() {
    $var = key($this->var);
     echo "当前元素的键: $var\n";
     return $var;
   }
 
   public function next() {
    $var = next($this->var);
     echo "移向下一个元素: $var\n";
     return $var;
   }
 
 
   public function valid() {
    $var = $this->current() !== false;
     echo "检查有效性: {$var}\n";
     return $var;
   }
}
 
 
$values = array(1,2,3);
$it = new MyIterator($values);
foreach ($it as $k => $v) {
   print "此时键值对 -- key $k: value $v\n\n";
}

Iterator extends Traversable {
  /* 方法 */
  abstract public mixed current ( void )//返回当前元素
  abstract public scalar key ( void )//返回当前元素的键
  abstract public void next ( void )//向前移动到下一个元素
  abstract public void rewind ( void )//返回到迭代器的第一个元素
  abstract public boolean valid ( void )//检查当前位置是否有效
}

class Season implements Iterator{
  private $position = 0;//指针指向0
  private $arr = array('春','夏','秋','冬');
  public function rewind(){
    return $this -> position = 0;
  }
  public function current(){
    return $this -> arr[$this -> position];
  }
  public function key(){
    return $this -> position;
  }
  public function next() {
    ++$this -> position;
  }
 
  public function valid() {
    return isset($this -> arr[$this -> position]);
  }
}
$obj = new Season;
foreach ($obj as $key => $value) {
  echo $key.':'.$value."\n";
}

class Fibonacci implements Iterator {
  private $previous = 1;
  private $current = 0;
  private $key = 0;
   
  public function current() {
    return $this->current;
  }
   
  public function key() {
    return $this->key;
  }
   
  public function next() {
    // 关键在这里
    // 将当前值保存到 $newprevious
    $newprevious = $this->current;
    // 将上一个值与当前值的和赋给当前值
    $this->current += $this->previous;
    // 前一个当前值赋给上一个值
    $this->previous = $newprevious;
    $this->key++;
  }
   
  public function rewind() {
    $this->previous = 1;
    $this->current = 0;
    $this->key = 0;
  }
   
  public function valid() {
    return true;
  }
}
 
$seq = new Fibonacci;
$i = 0;
foreach ($seq as $f) {
  echo "$f ";
  if ($i++ === 15) break;
}