[PSR-6] Decoupling CacheItem from CacheItemPool

[rindeal]

As already pointed out in #389, method exists() is the only method in CacheItemInterface which requires to know which CacheItemPool the item belongs to.

When trying to figure out, why exists() exists at all, I stumbled upon this article, which explains that the reason is memory efficiency for someone who just needs to peek into the cache to see if the item exists without caring what it's value is. To avoid race conditions the caller will also likely not use any other method provided in CacheItemInterface, unless he calls getItem() again.

To sum it up, I see no reason why exists() shouldn't be moved to CacheItemPoolInterface.

Note: the above text is copypasted from #609.

[Matteo Beccati]

Hi,

I agree. In fact I don't think the use cases are compelling enough to
have a separate non-atomic exists at all.

If we really want one though, it belongs to the pool.

On 24/08/2015 03:38, rindeal wrote:
> As already pointed out in #389

> <https://github.com/php-fig/fig-standards/issues/389>, method |exists()|

> is the only method in |CacheItemInterface| which requires to know which
> |CacheItemPool| the item belongs to.
>
> When trying to figure out, why |exists()| exists at all, I stumbled upon
> this article

> <http://blog.ircmaxell.com/2014/10/a-followup-to-open-letter-to-php-fig.html>,

> which explains that the reason is memory efficiency for someone who just
> needs to peek into the cache to see if the item exists without caring
> what it's value is. To avoid race conditions the caller will also likely

> not use any other method provided in |CacheItemInterface|, unless he

> calls |getItem()| again.
>
>
> To sum it up, I see no reason why |exists()| shouldn't be moved to
> |CacheItemPoolInterface|.
>
>
> Note: the above text is copypasted from #609

> <https://github.com/php-fig/fig-standards/issues/609>.
>
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--
Matteo Beccati

Development & Consulting - http://www.beccati.com/

[Robert Hafner]

I don’t care if it exists, but agree that moving it to the pool makes sense. So remove it to move it, I’m okay with either.

We’re not in review anymore, so make a pull request and we can see where this goes.

Rob

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[rindeal]

PR has been filled - https://github.com/php-fig/fig-standards/pull/612

[Paul Dragoonis]

On Tue, Aug 25, 2015 at 9:20 AM, Robert Hafner <ted...@tedivm.com> wrote:

I don’t care if it exists, but agree that moving it to the pool makes sense. So remove it to move it, I’m okay with either.

We’re not in review anymore, so make a pull request and we can see where this goes.

Rob

+1 on moving it back to where it belongs ;-)

 

To view this discussion on the web visit https://groups.google.com/d/msgid/php-fig/5CD8F955-88CB-4C1F-B307-3C61BCAFC1B5%40tedivm.com.

[rindeal]

As time went I made some deeper changes to the PR including a naming change (itemExists ---> hasItem) and related docs changes. Any feedback would be appreciated.