(PHP 5, PHP 7, PHP 8)
Interfaz para detectar si una clase puede recorrerse mediante foreach.
Una interfaz abstracta base no puede ser implementada sola. En su lugar, debe ser implementada con IteratorAggregate o con Iterator.
Esta interfaz no tiene métodos, su único propósito es ser la base para todas las clases atravesables.
| Versión | Descripción |
|---|---|
| 7.4.0 | La interfaz Traversable ahora puede ser implementada por clases abstractas. Las clases que la extiendan deben implementar Iterator o IteratorAggregate. |
Nota:
Las clases internas que implementan esta interfaz pueden ser usadas en una construcción foreach y no necesitan implementar IteratorAggregate o Iterator.
Nota:
Antes de PHP 7.4.0, esta interfaz interna del motor no podía ser implementada en scripts PHP. Se debe usar IteratorAggregate o Iterator deben usarse en su lugar.
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
?>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
threeThe 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.phpNote 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.