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References: <0047f3c7-3e9e-ef6f-2d7a-e58c316ea751@gmail.com>
In-Reply-To: <0047f3c7-3e9e-ef6f-2d7a-e58c316ea751@gmail.com>
Date: Sun, 21 Oct 2018 20:57:50 -0600
Message-ID: <CAFMT4NoK2CZshYsQ0sxeHLQ9_jewSAua8n8ah1NuNPdCcPRyYQ@mail.gmail.com>
To: Rowan Collins <rowan.collins@gmail.com>
Cc: internals <internals@lists.php.net>
Content-Type: text/plain; charset="UTF-8"
Subject: Re: [PHP-DEV] Composition over inheritance: native support for
 "delegating" methods?
From: levim@php.net (Levi Morrison)

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());
  }
}