Turn Traversable objects into Iterators. Fixed version of the native IteratorIterator

1.0.0 2017-06-17 16:55 UTC

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Last update: 2020-08-08 05:39:32 UTC


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Iterator that can be constructed from Traversable objects.

Can be seen as a fixed version of IteratorIterator (which is used internally). IteratorIterator behaves in unexpected ways when constructed from an IteratorAggregate: it only calls getIterator once rather than once per iteration, which is what happens when you traverse the IteratorAggregate directly. In other words: looping over an IteratorIterator that contains a IteratorAggregate yields different behaviour than looping over the IteratorAggregate itself. This is unexpected and can be problematic. For instance when the IteratorAggregate contains a Generator (which happens often), looping over the IteratorIterator more than once will cause an error due to the Generator not being rewindable.

Example of how IteratorIterator fails:

$iteratorAggregate = new class() implements \IteratorAggregate {
	public function getIterator() {
		yield 'a';
		yield 'b';
		yield 'c';

$iterator = new IteratorIterator( $iteratorAggregate );

foreach ( $iterator as $value ) {}
foreach ( $iterator as $value ) {} // Exception: Cannot rewind a generator that was already run

This exception, and more generally difference in behaviour, does not occur when using TraversableIterator.


To add this package as a local, per-project dependency to your project, simply add a dependency on wmde/traversable-iterator to your project's composer.json file. Here is a minimal example of a composer.json file that just defines a dependency on Traversable Iterator 1.x:

    "require": {
        "wmde/traversable-iterator": "~1.0"


Running the tests

For a full CI run

composer ci

For tests only

composer test

For style checks only

composer cs

Release notes

1.0.0 (2017-06-17)

  • Initial release