Gordon,

On Oct 12, 2005, at 10:48 AM, Gordon Henriksen wrote:
Actually, I wondered why you didn't suggest this earlier. :) I figured you were a step ahead of me: What if I want more than a boolean out of my class method?


Then you put the class methods back in :)

But then your Objective-C interface would need to change too. Although, the more complexity you introduce, the closer you get to the point when a Factory pattern is just as viable an approach as class methods.

Stevan

On Oct 12, 2005, at 10:27, Stevan Little wrote:
Gordon,

It just occurred to me that the system shown below could be re- written to do away with class methods entirely.

class Host {
    my $.plugInClass;
}

role PlugIn {
    method initWithHost (Host $h:) { ... }
}

role FeatureA {}
role FeatureB {}
role FeatureC {}

class AB {
    does PlugIn;
    does FeatureA;
    does FeatureB;
}

class ABC {
    does AB;
    does FeatureC;
}

Now later on, instead of asking the PlugIn if it "supportsFeatureB", you can just see if it does the "FeatureB" role, like this:

if ($host.plugInClass.does('FeatureB')) {
    # ... do something with FeatureB
}

This will work with the ABC plugin as well since AB is being treated as a role, ABC will actually consume all it's subroles, which means that ABC will DWIM too. In fact, we get even more from this system since we can check if one plug-in is capable of "doing" another, because this "just works"

if ($host.plugInClass.does('AB')) {
    # ...
}

And since an example is better when it is backed up by working code, I coded this up using the current meta-model prototype. You can see it here: http://svn.openfoundry.org/pugs/perl5/Perl6- MetaModel/t/38_PlugIn_example.t

Stevan




On Oct 12, 2005, at 9:41 AM, Stevan Little wrote:


class Host {
    my $.plugInClass;
}

role PlugIn {
    method initWithHost (Host $h:) { ... }
}

role SupportsFeatureA {
    # yes, this Role has a "class method" in it, which
    # the consuming class will get as a "class method"
    method supportsFeatureA (Class $c:) { bool::true }
}

role SupportsFeatureB {
    method supportsFeatureB (Class $c:) { bool::true }
}

class AB {
    does PlugIn;
    does SupportsFeatureA;
    does SupportsFeatureB;
}

role SupportsFeatureC {
    method supportsFeatureC (Class $c:) { bool::true }
}

class ABC {
    does AB;
    does SupportsFeatureC;
}








—

Gordon Henriksen
[EMAIL PROTECTED]





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