On Sunday, September 1, 2002, at 08:27 , Jeffry Houser wrote:
> I almost skipped over this post because it was all quotes. ( I imagine
> that was because the list was bouncing stuff for a bit).
Yeah, sorry about that.
> 3. Is the data created inside a component protected from outside
> forces? I'm a little grey on this one. You can create component specific
> variables using the this scope.
"this" scope is public, the unnamed scope is private so this gets a YES.
> 2. Do CFCs support Overloading / Overriding? Not in related objects.
Overloading no, overriding yes. (And I don't really agree that overloading
is actually *necessary* to claim 'OO-ness' - much of the worst code I have
seen in OO languages is because of overloading and there are almost always
ways around it).
> A child CFC inherits all parent
> methods as is. You do not have the ability to change functionality of
> inherited methods.
Yes you do. Try the following:
// base.cfc:
<cfcomponent>
<cffunction name="foo" returntype="string">
<cfreturn "I'm base.foo"/>
</cffunction>
</cfcomponent>
// derived.cfc:
<cfcomponent extends="base">
<cffunction name="foo" returntype="string">
<cfreturn "I'm derived.foo"/>
</cffunction>
</cfcomponent>
// test.cfm:
<cfset b = createObject("component","base")/>
<cfset d = createObject("component","derived")/>
<cfoutput>
b.foo() is #b.foo()#<br>
d.foo() is #d.foo()#<br>
</cfoutput>
You can pass d to anything expecting a base component instance so
substitutability is preserved and polymorphism is also preserved.
> 3. Do CFCs support inheritance? Yes, they do. However without the
> overloading / overriding it is nothing more than a fancy include.
Overloading is mostly irrelevant for inheritance - in most (all?) OO
languages, when you inherit an overloaded set of methods, you have to
reimplement all of them in order to preserve overloading - overloading
normally only occurs within each class definition.
As pointed out above, CFMX does have overriding so inheritance *is* more
than a fancy include.
> 4. Do CFCs support polymorphism? I would say no. I cannot create two
> different methods with the same exact name, but different argument
> types. That is the essence of polymorphism.
No, that is overloading. Polymorphism requires overriding - see above - so
CFMX *does* support polymorphism. Polymorphism is 'virtual functions' in
most every OO language, something that CFMX does have.
> For me, the lack of the ability to overload is what makes me
> say you cannot apply Object Oriented development
As I say above, overloading really has nothing to do with OO. C has
overloading (Oh, yes, it does! Check out the latest ISO C standard to see
how they worked that in. Not for all types, admittedly, but they did add
it).
(Do I need to mention that I wrote the first ANSI-validated C compiler,
spent eight years on the ISO C++ Standards Committee - three as secretary
- designing parts of that language and also worked on the UK and ISO Java
Study Groups for a couple of years as well? :)
Sean A Corfield -- http://www.corfield.org/blog/
"If you're not annoying somebody, you're not really alive."
-- Margaret Atwood
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