Detailed explanation of the internal execution process of PHP iterator

Detailed explanation of the internal execution process of PHP iterator_PHP tutorial

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Release： 2016-07-13 10:25:18

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复制代码代码如下:

class myIterator implements Iterator {
    private $position = 0;
    private $array = array(
        "first_element",
        "second_element",
        "last_element",
    );

    public function __construct() {
        $this->position = 0;
    }

    function rewind() {
        var_dump(__METHOD__);
        $this->position = 0;
    }

    function current() {
        var_dump(__METHOD__);
        return $this->array[$this->position];
    }

    function key() {
        var_dump(__METHOD__);
        return $this->position;
    }

    function next() {
        var_dump(__METHOD__);
        ++$this->position;
    }

    function valid() {
        var_dump(__METHOD__);
        return isset($this->array[$this->position]);
    }
}

$it = new myIterator;

foreach($it as $key => $value) {
echo '输出键值：';
var_dump($key, $value);
//echo $key;
echo "n";
}

程序运行输出：

复制代码代码如下:

string(18) "myIterator::rewind"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值：int(0)
string(13) "first_element"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值：int(1)
string(14) "second_element"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值：int(2)
string(12) "last_element"

string(16) "myIterator::next"
string(17) "myIterator::valid"

一般的迭代器内部需要下面的方法：
Iterator::current — Return the current element 返回当前元素
Iterator::key — Return the key of the current element 返回当前元素的键
Iterator::next — Move forward to next element 移向下一个元素
Iterator::rewind — Rewind the Iterator to the first element 重新回到第一个元素
Iterator::valid — Checks if current position is valid 检查当前位置的有效性
如果不是很清楚迭代器的内容工作流程，可以查看下面的迭代器对数组的遍历过程：

复制代码代码如下:

/**
* @author Simple Modern Magic http://www.nowamagic.net
*/
class MyIterator implements Iterator
{
private $var = array();

public function __construct($array)
{
if (is_array($array)) {
var = $array;
}
}

public function rewind() {
echo "Rewind the first element n";
reset($this->var);
}

public function current() {
$var = current($this->var);
echo "Current element: $varn";
return $var;
}

public function key() {
$var = key($this->var);
echo "The key of the current element: $varn";
return $var;
}

public function next() {
$var = next($this->var);
echo "Move to next element: $varn";
return $var;
}

public function valid() {
$var = $this->current() !== false;
echo "Check validity: {$var}n";
return $var ;
}
}

$values = array(1,2,3);
$it = new MyIterator($values);

foreach ($it as $k => $v) {
print >Program running result:

Copy code

The code is as follows:Rewind the first elementCurrent element: 1

Check validity: 1

Current element: 1
Key of current element: 0
Key-value pair at this time--key 0: value 1

Move to next element: 2
Current element: 2
Check validity: 1Current element: 2

Key of current element: 1
Key-value pair at this time - - key 1: value 2

Move to next element: 3
Current element: 3
Check validity: 1

Current element: 3

Key of current element: 2
Key-value pair at this time - - key 2: value 3

Move to next element:
Current element:
Check validity:

That’s clear now, right?

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