Re: Inheritance and Loaded Libraries
Re: Inheritance and Loaded Libraries
- Subject: Re: Inheritance and Loaded Libraries
- From: Christopher Nebel <email@hidden>
- Date: Mon, 1 Nov 2004 19:27:24 -0800
On Oct 28, 2004, at 1:40 PM, has wrote:
Paul Berkowitz wrote:
A script's parent property can hold any type of object. When a
script object receives a command it doesn't understand, it forwards
that command to the object stored in its parent property. This is
called 'delegation'.
I'm sure you're right. But AppleScript refers to it as "inheritance",
even if it shouldn't according to object-oriented languages (or you).
I know, and it's misleading. With inheritance-based composition, the
attributes defined in each class are all squidged together to define a
new kind of object. Individual objects can then be created using that
definition. With delegation-based composition, individual objects that
are already in existence are linked together as a chain, allowing
messages to pass automatically up and down that chain.
For what it's worth, the authors of Self refer to these as "class-based
inheritance" and "prototype-based inheritance", respectively. (See
<http://research.sun.com/self/papers/self-power.html>.) I'm not sure
if those terms are considered standard, but Self is one of the first
languages to use prototypes exclusively, so there you are.
--Chris Nebel
AppleScript Engineering
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