While you cannot implement this interface, you can use it in your checks to determine if something is usable in for each. Here is what I use if I'm expecting something that must be iterable via foreach.
<?php
if( !is_array( $items ) && !$items instanceof Traversable )
//Throw exception here
?>
Traversable 인터페이스
(PHP 5 >= 5.0.0, PHP 7)
소개
클래스가 foreach 로 순회가능할 경우 그것을 감지하는 인터페이스 입니다.
단독으로 구현될수 없는 추상 인터페이스 입니다. IteratorAggregate 또는 Iterator 를 구현하세요.
Note:
이 인터페이스를 구현한 내부(내장된) 클래스는 foreach 에 사용될수 있으며, IteratorAggregate 또는 Iterator를 구현할 필요가 없습니다.
Note:
내부 엔진 인터페이스이며 PHP 스크립트로 구현될수 없습니다. 반드시 IteratorAggregate 또는 Iterator 를 사용해야 합니다. Traversable를 상속한 인터페이스를 구현할때, implements 절에서 IteratorAggregate 나 Iterator를 그 인터페이스명 앞에 지정해 주시기 바랍니다.
인터페이스 개요
Traversable
{
}이 인터페이스는 메서드가 없습니다, 이 인터페이스는 모든 순회가능한 클래스들의 기본 인터페이스로만 존재합니다.
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User Contributed Notes 5 notes
kevinpeno at gmail dot com ¶
14 years ago
cobaltbluedw ¶
8 years ago
NOTE: While objects and arrays can be traversed by foreach, they do NOT implement "Traversable", so you CANNOT check for foreach compatibility using an instanceof check.
Example:
$myarray = array('one', 'two', 'three');
$myobj = (object)$myarray;
if ( !($myarray instanceof \Traversable) ) {
print "myarray is NOT Traversable";
}
if ( !($myobj instanceof \Traversable) ) {
print "myobj is NOT Traversable";
}
foreach ($myarray as $value) {
print $value;
}
foreach ($myobj as $value) {
print $value;
}
Output:
myarray is NOT Traversable
myobj is NOT Traversable
one
two
three
one
two
three
douglas at reith dot com dot au ¶
7 years ago
The PHP7 iterable pseudo type will match both Traversable and array. Great for return type-hinting so that you do not have to expose your Domain to Infrastructure code, e.g. instead of a Repository returning a Cursor, it can return hint 'iterable':
<?php
UserRepository::findUsers(): iterable
?>
Link: http://php.net/manual/en/migration71.new-features.php#migration71.new-features.iterable-pseudo-type
Also, instead of:
<?php
if( !is_array( $items ) && !$items instanceof Traversable )
//Throw exception here
?>
You can now do with the is_iterable() method:
<?php
if ( !is_iterable( $items ))
//Throw exception here
?>
Link: http://php.net/manual/en/function.is-iterable.php
ajf at ajf dot me ¶
9 years ago
Note that all objects can be iterated over with foreach anyway and it'll go over each property. This just describes whether or not the class implements an iterator, i.e. has custom behaviour.
alan dot bem at gmail dot com ¶
6 years ago
Actually you can use `Traversable` within your php scripts - you can use it to enforce iterability on user-land objects.
<?php
interface Stream implements \Traversable {}
class InMemoryStream implements IteratorAggregate, Stream
{
public function getIterator() {}
}
$stream = new InMemoryStream();
?>
In case you'd forgot about implementing `IteratorAggregate` or `Iterator` interfaces, fatal error will be raised when instantiating objects in question.
<?php
interface Stream implements \Traversable {}
class InMemoryStream implements Stream {}
$stream = new InMemoryStream(); // Fatal error: Class InMemoryStream must implement interface Traversable as part of either Iterator or IteratorAggregate in Unknown on line 0
?>
