類與物件(PHP5)之八：物件叠代(Object Iteration)
日期:2006-09-26 作者:喜騰小二 來源:PHPChina
PHP5提供一個為物件定義透過一連串的訊息被重述的途徑成為可能，例如使用一個foreach陳述式。預設地，所有可見的內容將用來叠代(反覆)。
例子
19-20. 簡單的物件叠代(Simple Object Iteration)
PHP程式碼如下:
php
class MyClass
{ public $var1 = 'value 1';
public $var2 = 'value 2';
public $var3 = 'value 3';
protected $protected = 'protected var';
private $private = 'private var';
function iterateVisible()
{ echo "MyClass::iterateVisible:
";
foreach($this as $key => $value){ print "$key => $value
"; }
}
}
$class = new MyClass();
foreach($class as $key => $value){ print "$key => $value
"; }
echo "
";
$class->iterateVisible();
?>
如輸出顯示，foreach重述能透過全部可見變數被訪問。更進一步，妳可以實現一個PHP5的指定的內在介麵叠代器(Iterator)。允許物件描述什麼是物件重述和物件如何被重述的。
例子
19-21. 叠代器實現物件叠代(Object Iteration implementing Iterator)
PHP程式碼如下:
php
class MyIterator implements Iterator
{ private $var = array();
public function __construct($array)
{ if (is_array($array)){ $this->var = $array; }
}
public function rewind()
{ echo "rewinding
";
reset($this->var);
}
public function current()
{ $var = current($this->var);
echo "current: $var
";
return $var;
}
public function key()
{ $var = key($this->var);
echo "key: $var
";
return $var;
}
public function next()
{ $var = next($this->var);
echo "next: $var
";
return $var;
}
public function valid()
{ $var = $this->current() !== false;
echo "valid: {$var}
";
return $var;
}
}
$values = array(1,2,3);
$it = new MyIterator($values);
foreach ($it as $a => $b) { print "$a: $b
"; }
?>
上例將輸出：
CODE:
rewinding
current: 1
valid: 1
current:
1
key: 0
0: 1
next: 2
current: 2
valid: 1
current: 2
key:
1
1: 2
next: 3
current: 3
valid: 1
current: 3
key: 2
2:
3
next:
current:
valid:
在定義類時妳也可以不必透過簡單實現PHP5的IteratorAggregate介麵定義所有的叠代器函式。
例19-22.IteratorAggregate物件叠代實現
PHP程式碼如下:
php
class MyCollection implements IteratorAggregate
{ private $items = array();
private $count = 0;
// Required definition of interface IteratorAggregate
public function getIterator()
{ return new MyIterator($this->items);
}
public function add($value)
{
$this->items[$this->count++] = $value;
}
}
$coll = new MyCollection();
$coll->add('value 1');
$coll->add('value 2');
$coll->add('value 3');
foreach ($coll as $key => $val){ echo "key/value: [$key -> $val]
"; }
?>
上例將輸出：
[Copy to clipboard]CODE:
rewinding
current: value 1
valid:
1
current: value 1
key: 0
key/value: [0 -> value 1]
next: value
2
current: value 2
valid: 1
current: value 2
key: 1
key/value: [1
-> value 2]
next: value 3
current: value 3
valid: 1
current:
value 3
key: 2
key/value: [2 -> value
3]
next:
current:
valid:
|
|
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