Re: Generics proposal
| From: | jpauli | Date: | Mon, 22 Oct 2012 16:25:48 +0000 |
| Subject: | Re: Generics proposal | ||
| References: | 1 | Groups: | php.internals |
| Request: | Send a blank email to internals+get-63600@lists.php.net to get a copy of this message | ||
On Sat, Oct 20, 2012 at 10:59 PM, Nikita <inefedor@gmail.com> wrote:
> Hello, list. I want to propose generics. For those, who don't know what it is, here's
> example: say we have a Comment class, that has a method getBody. Also we have Collection class, that
> implements Traversable. Now, if I want to validate all insertions into collection of comments, I
> would need to create CommentCollection class, extend it from Collection, and override all the
> methods that are dealing with adding new elements to collection. Moreover, I can't have any
> hints from my IDE about type of collection's elements, so if I'll have code like this:
> foreach ($commentCollection as $comment) {
> $comment->getBody();
> }
> There will be no way for IDE to know, of what type that object will be.
>
> But there's how I could solve my problem with generics:
> class Collection<T> implements Traversable
> {
> ...
> public function add(T $element){}
> }
> $collection = new Collection<Comment>();
>
> $collection->add(new Comment());
>
> $collection->add("that will be error");
>
> Actually, that's, again, all about type hinting. If we went so far with scalar type
> hinting, then generics would also be a good addition.
>
> So, what you think?
Hah, I had the use case often, and every OO programmer has met this
use case several time I think :
Here is an example with SplObjectStorage (which is a good starting
point structure for that) :
<?php
class MyClass extends SPlObjectStorage
{
public function attach(MyType $o, $data = null) { /* throws an
E_STRICT we all know about */
return parent::attach($o, $data);
}
}
Solution :
<?php
class MyClass extends SPlObjectStorage
{
public function attach($o, $data = null) {
if (!$o instanceof MyType) { /* That is both ugly and boring
to write */
throw new \RuntimeException();
}
return parent::attach($o, $data);
}
}
So, I'm +1 with the idea, but -1 with the proposed syntax.
I'm +1 with Lars, as this can be done with a "TypeAsString", this is
as well ugly, and I think we need PHP to provide a way to do that :
<?php
class Foo
{
public function __construct($type) { $this->type = $type; }
public function add($o)
{
if (!$o instanceof $this->type) {
throw new \RunTimeException("type {$this->type} expected");
}
/* do something with $o*/
}
}
class Bar { }
class Baz { }
$f = new Foo('bar');
$f->add(new Bar); /* OK */
$f->add(new Baz); /* KO */
$f->add(array()); /* KO */
?>
IMO : this is something the language should take care of, not the
developper, but that's my opinion :)