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Separating Concerns Using Object Add-Ons
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(NEW in version 0.6: the``Registry`` base class, and the
``ClassAddOn.for_frame()`` classmethod.)
In any sufficiently-sized application or framework, it's common to end up
lumping a lot of different concerns into the same class. For example, you
may have business logic, persistence code, and UI all jammed into a single
class. Attribute and method names for all sorts of different operations get
shoved into a single namespace -- even when using mixin classes.
Separating concerns into different objects, however, makes it easier to write
reusable and separately-testable components. The AddOns package
(``peak.util.addons ...