Re: [PHP-DEV] Interface inheritance

[George Schlossnagle]

On Apr 20, 2004, at 10:48 AM, Ferdinand Beyer wrote:

On 20 Apr 2004 at 17:38, Stanislav Malyshev wrote:

FB>>interface A {
FB>>    public function doSomething($integer1, $integer2);
FB>>}
FB>>
FB>>interface B {
FB>>   public function doSomething(MyObject $obj);
FB>>}
FB>>
FB>>class Impl implements A, B
FB>>{
FB>>    // "Overloaded" - supports both doSomething() interfaces
FB>>    public function doSomething()
FB>>    {
FB>>        // Use var_args to distinquish the two doSomething()'s
FB>>    }
FB>>}
The problem here that you can't know if Impl would actually accept
MyObject or two integers as arguments. So if some method
requires object
with interface A and it's passed Impl, it cannot actually be sure it
can
use it as an A object.
Impl guarantees that by implementing interface A.

What if Impl::doSomething() would accept exactly two parameters,
but expects them to be arrays?
IMO you cannot enforce this strictness with loose types...
This is probably a bad argument since while PHP doesn't currently allow 
type hinting based on whether a parameter is an array vs. a scalar, 
it's technically feasible and their is no good auto-casting from array 
to scalar or vice-versa.  A better argument is expecting different 
types of scalars.  That would be much harder with PHP's typing 
semantic.

George

--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: http://www.php.net/unsub.php