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IteratorAggregate（聚合式迭代器）接口

(PHP 5, PHP 7, PHP 8)

简介

创建外部迭代器的接口。

接口摘要

interface IteratorAggregate extends Traversable {

/* 方法 */

public getIterator(): Traversable

}

示例 #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 $property4 = "";

    public function __construct() {
        $this->property4 = "last property";
    }

    public function getIterator(): Traversable {
        return new ArrayIterator($this);
    }
}

$obj = new myData;

foreach($obj as $key => $value) {
    var_dump($key, $value);
    echo "\n";
}
?>

以上示例的输出类似于：

 
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"

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);
}
?>

down

Tab Atkins ¶

11 years ago

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.

down

Lubaev.K ¶

10 years ago

<?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!

down

Martin Speer ¶

4 years ago

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 
 */ ?>

down

-14

ribeirocfb at gmail dot com ¶

8 years ago

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"
*/

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IteratorAggregate（聚合式迭代器）接口

简介

接口摘要

目录

User Contributed Notes 5 notes