is_array on objects with ArrayAccess or Iterator implementations View as Markdown

Hi,

Etienne Kneuss wrote:

On Tue, Dec 29, 2009 at 12:04 AM, Clint Priest cpriest@warpmail.net
wrote:

Unfortunately $x instanceOf ArrayAccess doesn't return true when $x is
indeed an array.

Making is_array return true for objects implementing ArrayAccess is a
bad idea, for two main reasons:

1. is_array is a type check, and we should still be able to
   distinguish real arrays from objects

That's true of course, definitely would need to be able to distinguish.

2. ArrayAccess does not guarantee that an object will behave like an
   array, (e.g. you won't be able to use sort() on an object implementing
   ArrayAccess.

I wonder if this is something that users would be expecting, that any
function which took an array would also take an object that implements
certain interfaces (such as ArrayAccess and perhaps Countable).

If, in your case, you want to accept both arrays and ArrayAccess
objects, I guess if (is_array($v) || $v instanceof ArrayAccess)  is a
sufficiently good way to check.

I'm finding myself implementing ArrayAccess more and more often because its
so transparent to the consumer.  The reason this came up is because I was
considering returning all arrays from a certain section of my shared code
library always be an array object so that things like
$tblArray->pluck('Value') could be done, rather than array_pluck() type
functionality.

That got me to thinking about all of the is_array() calls I would need to
replace throughout the codebase.

Would it be terribly difficult to make objects with ArrayAccess completely
interchangable anywhere an array element would be required by a function?

Yes, definitely, it would be a quite big amount of work (basically
rewriting every functions dealing with arrays), and the interface that
ArrayAccess proposes isn't enough for most array tasks.

--
Etienne Kneuss
http://www.colder.ch

Etienne Kneuss wrote:

On Tue, Dec 29, 2009 at 12:04 AM, Clint Priest
cpriest@warpmail.net wrote:

Unfortunately $x instanceOf ArrayAccess doesn't return true when $x
is
indeed an array.

Making is_array return true for objects implementing ArrayAccess is
a
bad idea, for two main reasons:

1. is_array is a type check, and we should still be able to
   distinguish real arrays from objects
   That's true of course, definitely would need to be able to
   distinguish.

is_array is precisely what we expect to be able to use to distinguish.

2. ArrayAccess does not guarantee that an object will behave like an
   array, (e.g. you won't be able to use sort() on an object
   implementing
   ArrayAccess.
   I wonder if this is something that users would be expecting, that any
   function which took an array would also take an object that implements
   certain interfaces (such as ArrayAccess and perhaps Countable).

Certainly if is_array returns TRUE, I would expect it to be an
array, and do what a PHP array is supposed to do. :-)

If, in your case, you want to accept both arrays and ArrayAccess
objects, I guess if (is_array($v) || $v instanceof ArrayAccess) is
a
sufficiently good way to check.

A simple one-liner:
function is_arrayaccess ($object){
return (is_array($object) || $object instanceof ArrayAccess);
}

and a global search and replace for is_array should not tax your
resources.

Another option is to have a class that implements ArrayAccess in the
simplest easiest way, by having a private property which is a true
is_array() built-in, and all the methods just work on that private
property.

You can pass that out from your library, and internally it can use the
array itself. You may even find a combination of private/protected
that lets you expose the internal array when it is desirable to access
it directly.

Would it be terribly difficult to make objects with ArrayAccess
completely interchangable anywhere an array element would be required
by
a function?

Even if you could guarantee that every function would "work" it's
still a Bad Idea.

What are you going to do about var_dump and print_r?

Are they going to lie to me and tell me it's an array and print it out
exactly like an array?

Or is it going to distinguish, as it should?

No matter how much you love ArrayAccess, it's not an array. It's a
class that implements specific array-like feature set.