问题描述
如果我有一个实现 Iterator 接口的类，我可以手动控制 foreach 循环中的迭代方式.但是还有其他方法可以让我的对象表现得像一个数组吗?
If I have a class that implements the Iterator interface, I can manually control how iteration in a foreach loop. But are there other ways in which I could make my object behave like an array?
例如，假设我有一个实现 Iterator 的类 Guestbook，这样我就可以迭代 foreach (new Guestbook() as $entry).但是，如果我想颠倒顺序怎么办?
For instance, let's say I have a class Guestbook which implements Iterator, so that I can iterate foreach (new Guestbook() as $entry). But what if I want to, say, reverse the order?
foreach (array_reverse(new Guestbook()) as $entry) 肯定不行，因为 array_reverse 只接受一个数组.
foreach (array_reverse(new Guestbook()) as $entry) definitely won't work, because array_reverse will only accept an array.
我想我想问的是，我可以将 Iterator 用于更多的 foreach 循环吗?
I guess what I'm asking is, can I use Iterator for more than just foreach loops?
谢谢.
推荐答案
迭代器接口的目的 是为了让你的对象在 foreach 循环中使用，它不是为了让你的对象像一个数组.如果您想要一些像数组一样的东西，请使用数组.
The purpose of the Iterator interface is to allow your object to be used in a foreach loop, it is not intended to make your object act like an array. If you want something that acts like an array, use an array.
您始终可以使用iterator_to_array 函数将您的对象转换为数组，但您无法逆转该过程.
You can always turn your object into an array by using the iterator_to_array function, but you can't reverse that process.
如果您认为需要反转可迭代对象中元素的顺序，那么您可以创建一个 reverse() 方法，该方法可能在内部使用 array_reverse().像这样:-
If you see the need for reversing the order of the elements in your iterable object, then you could create a reverse() method that, possibly, uses array_reverse() internally. Something like this:-
class Test implements Iterator
{
private $testing = [0,1,2,3,4,5,6,7,8,9,10];
private $index = 0;
public function current()
{
return $this->testing[$this->index];
}
public function next()
{
$this->index ++;
}
public function key()
{
return $this->index;
}
public function valid()
{
return isset($this->testing[$this->key()]);
}
public function rewind()
{
$this->index = 0;
}
public function reverse()
{
$this->testing = array_reverse($this->testing);
$this->rewind();
}
}
$tests = new Test();
var_dump(iterator_to_array($tests));
$tests->reverse();
var_dump(iterator_to_array($tests));
输出:-
array (size=11)
0 => int 0
1 => int 1
2 => int 2
3 => int 3
4 => int 4
5 => int 5
6 => int 6
7 => int 7
8 => int 8
9 => int 9
10 => int 10
array (size=11)
0 => int 10
1 => int 9
2 => int 8
3 => int 7
4 => int 6
5 => int 5
6 => int 4
7 => int 3
8 => int 2
9 => int 1
10 => int 0
我写了代码是为了在发布之前向自己证明它可以工作，并认为我不妨把它扔到答案中.
I wrote the code to prove to myself that it would work before posting and thought I might as well throw it into the answer.
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