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创建外部迭代器的接口。
Example #1 基本用法
<?php
class myData implements IteratorAggregate {
public $property1 = "Public property one";
public $property2 = "Public property two";
public $property3 = "Public property three";
public function __construct() {
$this->property4 = "last property";
}
public function getIterator() {
return new ArrayIterator($this);
}
}
$obj = new myData;
foreach($obj as $key => $value) {
var_dump($key, $value);
echo "\n";
}
?>
以上例程的输出类似于：
string(9) "property1" string(19) "Public property one" string(9) "property2" string(19) "Public property two" string(9) "property3" string(21) "Public property three" string(9) "property4" string(13) "last property"
You can use yield from in getIterator in recent PHP 7 versions:
<?php
class Example implements \IteratorAggregate
{
protected $data = [];
public function __construct(array $data)
{
$this->data = $data;
}
public function getIterator()
{
yield from $this->data;
}
}
$test = new Example([1, 2, 3]);
foreach ($test as $node) {
echo $test, PHP_EOL;
}
/*
* Outputs:
*
* 1
* 2
* 3
*/ ?>
It might seem obvious, but you can return a compiled generator from your IteratorAggregate::getIterator() implementation.
<?php
class Collection implements IteratorAggregate
{
private $items = [];
public function __construct($items = [])
{
$this->items = $items;
}
public function getIterator()
{
return (function () {
while(list($key, $val) = each($this->items)) {
yield $key => $val;
}
})();
}
}
$data = [ 'A', 'B', 'C', 'D' ];
$collection = new Collection($data);
foreach ($collection as $key => $val) {
echo sprintf("[%s] => %s\n", $key, $val);
}
?>
Example of the Iterator Pattern
<?php
namespace DesignPaterns;
class BookCollection implements \IteratorAggregate
{
private $a_titles = array();
public function getIterator()
{
return new BookIterator($this);
}
public function addTitle($string)
{
$this->a_titles[] = $string;
}
public function getTitle($key)
{
if (isset($this->a_titles[$key])){
return $this->a_titles[$key];
}
return null;
}
public function is_empty()
{
return empty($a_titles);
}
}
<?php
namespace DesignPaterns;
class BookIterator implements \Iterator
{
private $i_position = 0;
private $booksCollection;
public function __construct(BookCollection $booksCollection)
{
$this->booksCollection = $booksCollection;
}
public function current()
{
return $this->booksCollection->getTitle($this->i_position);
}
public function key()
{
return $this->i_position;
}
public function next()
{
$this->i_position++;
}
public function rewind()
{
$this->i_position = 0;
}
public function valid()
{
return !is_null($this->booksCollection->getTitle($this->i_position));
}
}
<?php require 'vendor/autoload.php';
use DesignPaterns\BookCollection;
$booksCollection = new BookCollection();
$booksCollection->addTitle('Design Patterns');
$booksCollection->addTitle('PHP7 is the best');
$booksCollection->addTitle('Laravel Rules');
$booksCollection->addTitle('DHH Rules');
foreach($booksCollection as $book){
var_dump($book);
}
/* === Output ===
* string(15) "Design Patterns"
* string(16) "PHP7 is the best"
* string(13) "Laravel Rules"
* string(9) "DHH Rules"
*/
<?php
// IteratorAggregate
// Create indexed and associative arrays.
class myData implements IteratorAggregate {
private $array = [];
const TYPE_INDEXED = 1;
const TYPE_ASSOCIATIVE = 2;
public function __construct( array $data, $type = self::TYPE_INDEXED ) {
reset($data);
while( list($k, $v) = each($data) ) {
$type == self::TYPE_INDEXED ?
$this->array[] = $v :
$this->array[$k] = $v;
}
}
public function getIterator() {
return new ArrayIterator($this->array);
}
}
$obj = new myData(['one'=>'php','javascript','three'=>'c#','java',], /*TYPE 1 or 2*/ );
foreach($obj as $key => $value) {
var_dump($key, $value);
echo PHP_EOL;
}
// if TYPE == 1
#int(0)
#string(3) "php"
#int(1)
#string(10) "javascript"
#int(2)
#string(2) "c#"
#int(3)
#string(4) "java"
// if TYPE == 2
#string(3) "one"
#string(3) "php"
#int(0)
#string(10) "javascript"
#string(5) "three"
#string(2) "c#"
#int(1)
#string(4) "java"
?>
Good luck!
Note that, at least as of 5.3, you still aren't allowed to return a normal Array from getIterator().
In some places, the docs wrap the array into an ArrayObject and return that. DON'T DO IT. ArrayObject drops any empty-string keys on the floor when you iterate over it (again, at least as of 5.3).
Use ArrayIterator instead. I wouldn't be surprised if it didn't have its own set of wonderful bugs, but at the very least it works correctly when you use it with this method.