Re: initializing classes

On Tue, Mar 23, 2021 at 11:55 PM <[email protected]> wrote:
> Often it is better and more maintable to use object
> composition ("has-a") instead of inheritance ("is-a")

Fully agreed -- SC does "is-a" way too much, leading users to believe
that "is-a" is the best way (or even the only way). (For instance, I
haven't seen that question in a while, but it does come up from time
to time: "How to subclass a GUI view?" The best answer is usually:
Don't subclass, use SCViewHolder instead.)

That's not to say that subclassing is always a bad idea -- I'm just
re-emphasizing that, when we want to extend the behavior of an
existing class, often we reach first for a subclass, but just as
often, it's probably better to reach first for an Adapter or other
form of object composition.

> Finally, I would like to point out that you don't have to use sclang's
> class system (= classic inheritance), you can also build your object
> system with Events (= prototypical inheritance). Check out the
> documentation of IdentityDictionary - especially the "parent" and
> "proto" properties - for more information on this.

Or the ddwPrototype quark, which makes ~environmentVars local to the
prototype object, so, a bit more transparently object-like then Event
prototypes. (Over ten thousand lines of Proto-based code in the .scd
files here, if you want to see what that looks like --
https://github.com/jamshark70/ddwChucklib-livecode/ .)

hjh

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