Daniel Ruoso wrote:
> Jon Lang wrote:
>> Note that this ought only be true of class inheritance; with role
>> composition, there should only be one $!bar in the class, no matter
>> how many roles define it.
>
> er... what does that mean exactly?
Unless something has drastically changed since I last checked the
docs, roles tend to be even more ethereal than classes are. You can
think of a class as being the engine that runs objects; a role, OTOH,
should be thought of as a blueprint that is used to construct a class.
Taking your example:
> role B {
> has $!a;
> }
>
> role C {
> has $!a;
> }
>
> class A does B, C {
> method foo() {
> say $!a;
> }
> }
>
> I think in this case $!B::a and $!C::a won't ever be visible, while the
> reference to $!a in class A will be a compile time error.
:snip:
> Or does that mean that
>
> class A does B, C {...}
>
> actually makes the declarations in B and C as if it were declared in the
> class A?
Correct. Declarations in roles are _always_ treated as if they were
declared in the class into which they're composed. And since only
classes are used to instantiate objects, the only time that a role
actually gets used is when it is composed into a class.
--
Jonathan "Dataweaver" Lang
