Re: Composition over inheritance: native support for "delegating" methods?

I have wanted something like this before. I used a trait helper. This worked for this domain because there is an interface that is well established for the helper to use. Here's an example (written in my email client, untested): trait OuterIteratorHelper { abstract function getInnerIterator(): \Iterator; function rewind(): void { $this->getInnerIterator()->rewind(); } function valid(): bool { return $this->getInnerIterator()->valid(); } function next(): void { $this->getInnerIterator()->next(); } function key() { return $this->getInnerIterator()->key(); } function current() { return $this->getInnerIterator()->current(); } } final class TransformIterator implements \OuterIterator { private $transformer, $inner; function __construct(callable $transformer, \Iterator $inner) { $this->transformer = $transformer; $this->inner = $inner; } use OuterIteratorHelper; function getInnerIterator() { return $this->inner; } function current() { return ($this->transformer)($this->inner->current()); } }