[Zope3-dev] Re: Zope3 magic makes me cranky.

[Jim Fulton]

Fred L. Drake, Jr. wrote:
> Shane Hathaway writes:
>  > In any case, magically generating classes is crossing a line, don't you 
>  > think?  It's especially bad if the class pretends to have been loaded 
>  > from a Python module.  There must be a better way.
> 
> I'd certainly prefer to see a normal factory involved, though I think
> what's happening in the <page> directive is this:  The class attribute
> of the directive can specify a class which may not inherit from one of
> the page view classes (or implement the right interface), in which
> case it is mixed-in with a common classes that implements all the
> basic stuff.  This is inherantly asking for a disaster, I think.
> 
> But I think this was something that Jim wanted to support easier
> entrance to using Zope 3.  If we can convince him that this is
> misguided, that would be a good thing, and would allow a lot of
> simplification in this case.  And we wouldn't need such magically
> incanted classes.

It's not fun being channeled.

Here are the *real* reasons for generating a class:

- We want to be able to give a page a permission.
   This means that we need to associate a security
   checker with the view that ultimately gets created.
   The simplest way to do this is to generate a class,
   but it's not the only way to do it.

- We want to be able to specify a template in ZCML.
   The template needs to function as a method of the view.
   It is a descriptor.  Python doesn't support instance
   descriptors. We need to install it in a class, but, of
   course, we can't install it in the original class.

   There is probably some other way to do this.

The fact that less ceremony is needed in view classes is,
IMO, a valuable bonus.

Jim

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