[ I S]上午班 老師有東西漏講了
Mixin
In object-oriented programming languages, a mixin is a class that provides
a certain functionality to be inherited by a subclass, but is not meant to
stand alone. Inheriting from a mixin is not a form of specialization but is
rather a means to collect functionality. A class may inherit most or all of
its functionality by inheriting from one or more mixins through
multiple inheritance.
Mixins first appeared in the Symbolics' object-oriented Flavors system,
which was an approach to object-orientation used in Lisp Machine Lisp.
The name was inspired by Steve's Ice Cream Parlor in Somerville,
Massachusetts: The ice cream shop owner offered a basic flavor of ice cream
(vanilla, chocolate, etc.) and blended in a combination of extra items
(nuts, cookies, fudge, etc.) and called the item a "Mix-In",
his own trademarked term at the time.
Mixins encourage code reuse and avoid well-known pathologies associated with
multiple inheritance. However, mixins introduce their own set of compromises.
A mixin can also be viewed as an interface with implemented methods.
When a class includes a mixin, the class implements the interface and includes,
not inherits, all the mixin's attributes and methods. They become part of
the class during compilation. Interestingly enough mixins don't need to
implement an interface. The advantage of implementing an interface is that
instances of the class may be passed as parameters to methods requiring that
interface.
A mixin can defer definition and binding of methods until runtime,
though attributes and instantiation parameters are still defined at compile
time. This differs from the most widely-used approach, which originated
in the programming language Simula, of defining all attributes, methods
and initialization at compile time.
http://en.wikipedia.org/wiki/Mixin
ps 老師要我告訴上午班同學"Mixin"沒講到
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05/13 18:49, , 1F
05/13 18:49, 1F