It says, Apply the roles to the class at new time:

That does look like a good way to do it, in letting the user specify which extensions to use when creating the object. I don't have to imitate Catalyst's syntax or pass them as arguments to the new method.

But, I'm still composing it before construction. Consider a main class C1 which contains instances of C2 and C3 which it creates and holds on to. If all that's already been created, I can "patch" all three objects. If I derive an anonymous class and then instantiate it, the amendment for C1 has to include instructions to make it change what it creates for C2 and C3.

Now adding a role can do everything a traditional derived class can do, right? So there is no need to provide a mechanism to say "use this derived class instead of C2" in addition to the mechanism that lists all the roles that are to be applied to C2 at creation time.

I could have the builder that instantiates C2 consult an attribute that says what roles to add to it, and the original plug-in added to that list. But, I don't like the idea of having a field that doesn't do anything except during object creation. There should be a more transient way to pass the information around.

Maybe the builder can call something which gathers the trait's names, and the original plug-in can supply 'before' methods to grow that list. (But if I only have one instance anyway, all the extra code is worse than having a defunct slot!)

Any more suggestions?

In reply to Re^2: Extensions via Moose by John M. Dlugosz
in thread Extensions via Moose by John M. Dlugosz

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