为类 php 配置自己的迭代器？

Question

我有一个班级 Foo，我需要做：

$foo = new Foo();
foreach($foo as $value)
{
    echo $value;
}

并定义我自己的方法来迭代这个对象，例如：

class Foo
{
    private $bar = [1, 2, 3];
    private $baz = [4, 5, 6];


    function create_iterator()
    {
        //callback to the first creation of iterator for this object
        $this->do_something_one_time();
    }

    function iterate()
    {
        //callback for each iteration in foreach
        return $this->bar + $this->baz;
    }
}

我们可以这样做吗？怎么样？

Answer 1

你需要实现Iterator接口。

class Foo implements Iterator {

您应该查看内置接口：

http://php.net/manual/en/reserved.interfaces.php

Answer 2

您需要实现\Iterator 或\IteratorAggregate 接口来实现。

您尝试使用 \IteratorAggregate 和 \Iterator 接口实现的简单示例（我省略了 \Iterator 实现细节，但您可以使用 PHP 文档查看它们的工作原理）：

class FooIterator implements \Iterator
{
    private $source = [];

    public function __construct(array $source) 
    {
        $this->source = $source;
        // Do whatever else you need
    }

    public function current() { ... }
    public function key() { ... }
    public function next() 
    {
        // This function is invoked on each step of the iteration
    }
    public function rewind() { ... }
    public function valid() { ... }
}


class Foo implements \IteratorAggregate
{
    private $bar = [1, 2, 3];
    private $baz = [4, 5, 6];

    public function getIterator()
    {
        return new FooIterator(array_merge($this->bar, $this->baz));
    }
}

$foo = new Foo();

foreach ($foo as $value) {
    echo $value;
}