From: Jesse Luehrs <[email protected]>
>To: Pedro Melo <[email protected]>
>Cc: moose <[email protected]>
>Sent: Friday, 1 March 2013, 18:05
>Subject: Re: Role1 with attribute matches requires on Role2
>
>On Fri, Mar 01, 2013 at 04:56:57PM +0000, Pedro Melo wrote:
>> Hi,
>>
>> I keep getting bitten by this, and I was wondering if this is
>> something that will be solved eventually, or its something that would
>> be nice to solve but it is actually tricky to do, or just that I'm
>> doing it wrong.
>>
>> I have two roles, R1 and R2. R1 defines a attribute ctx. R2 requires a 'ctx'.
>>
>> If I use the two roles on a class C, with a single "with 'R1', 'R2';" I get
>>
>> 'R1|R2' requires the method 'ctx' to be implemented by 'C'
>>
>> I can work around it with two "with 'R1'; with 'R2';". But I loose all
>> the other protections wrt duplicate methods I might have in R1 and R2.
>>
>> Opinions?
>
>This is something that we'd like to fix - the problem is mainly that
>role accessors aren't generated until they are composed into a class,
>but role application composes roles together before composing them into
>the class. What we really need to do is provide a way for roles to say
>"I'm going to generate a method of this name", which we would be able to
>query during the role summation process (we can't actually generate the
>methods themselves because doing so requires an instance metaclass,
>which only classes have).
>
>Patches to fix this would be appreciated.
Out of curiosity, how is this handled in the internals? Does the role
composition do a simple ->can() check for methods? If so, during composition,
could has() fake a forward declaration?
{
package Foo;
sub bar;
}
say "yes" if Foo->can('bar');
You're not actually creating the method yet, but you're promising that it will
be there.
Cheers,
Ovid
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