Re: [RFC] Using objects as keys

Lester Caine wrote on 30/10/2014 16:44:

On 30/10/14 15:06, Rowan Collins wrote:

On 30 October 2014 10:40:10 GMT, Lester Caine <lester@lsces.co.uk> wrote:

On 30/10/14 07:19, Will Fitch wrote:

The magic method is more of a PHP approach while an interface would

be more appropriate. That said, this RFC is a true representation of a hash vs something like spl_object_hash. That’s what causes user confusion. spl_object_hash would’ve been better served as a name like spl_object_id or spl_object_hash_id. Something that indicates uniqueness regardless of the values of a particular object. The bit of the jigsaw I'm still missing here is just what the object of the exercise is?

There are many different use cases for hash keys, and PHP's "array" type is particularly flexible. For instance, de-duplicating a list of items ($foo[$x] = $x), or counting occurrences of each ($foo[$x]++) In the case of a simple DB model, the primary key value is the obvious choice for the hash key, but not all objects are as simple as that. Being able to store the object itself would save having to recreate it from the key, e.g. looking the ID back up for a DB model, or re-parsing UTF8 for a UString.

But that statement makes no sense! Accessing the object is via a handle, so you will always have a pointer to it. Adding some abstract identifier to describe the pointer is always going to be secondary to the pointer itself? You need a name to create an object and creating an array of objects needs keys which can either just be the PHP default location in the array, or you add a name to that key in some way. The content of the location in the array is the handle to the object. It will never be 'the object'? To look up an object you need to know something about the object and that is either some subset of the object or an abstract reference which one looks up in order to access the pointer.

I think you may be confusing two things here - one is storing objects as the *values* of an associative array, and choosing an appropriate key to use for each object; the other is using objects (or some representation of objects) as the *keys* of an associative array, with something completely different as the value. Yes, by "the object itself" I mean a pointer to the object, as most people do when talking colloquially about "passing objects around", etc. The point is to store a live reference, as opposed to a string or integer which could, programmatically, be used to look up/recreate the object. The use case which came up recently was UString objects, which can easily be converted to and from plain PHP strings, but would be useful as keys in their own right. With current PHP you could do $foo[ (string)$u_str ] = $bar; with the proposed RFC, you could do $foo[ $u_str ] = $bar with the same result; but either way, you would still need to convert *back* to an object in order to use any of the UString methods in a foreach(), array_walk(), etc. -- Rowan Collins [IMSoP]