Jon, indeed you are correct with that example. I see i've been trying to do something
slightly different, following, or maybe misfollowing, the Template Method pattern
article in CFDJ - and that created part of the impression.
<cfcomponent name="Parent" >
<cffunction name="init" access="public" returntype="any">
<cfset Variables.Name = "I'm an object in a family" >
<cfset variables.theChild = createObject('component','Child')>
<cfreturn this />
</cffunction>
<cffunction name="getChild" access="public" returntype="any">
<cfreturn variables.theChild>
</cffunction>
</cfcomponent>
<cfcomponent name="Child" extends="Parent">
<cffunction name="GetName" >
<cfreturn Variables.Name >
</cffunction>
</cfcomponent>
<cfset family = theParent.getChild().GetName() />
This gives me an "Element NAME is undefined in VARIABLES" error on the GetName method.
So I see you can't "combine" inheritance and composition now in this way. The child
element needs to be instantiated outside of the parent element, probably in the same
variable space. I wasn't so clear about that until now.
Thanks! That cleared something else up for me!
:^) <sporting-bright-nosed-grin>
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Jon Gunnip
Sent: Monday, December 08, 2003 4:08 PM
To: [EMAIL PROTECTED]
Subject: RE: [CFCDev] Difficulty in getting the light bulb to turn on...
>>> [EMAIL PROTECTED] 12/08/03 03:04AM >>>
> Another is that i'm beginning to see that inheritance is "nearly useless" in CF -
> well, that's a broad statement, but for the most part it's kinda true, because all
> that is inherited is the methods. The instance data isn't inherited, because it's
only
> class inheritance, not object inheritance. So if you need the instance data in the
> subtypes, and you probably will, you still need to pass it down to the subtype using
> ... you got it, composition.
Component data (vars in the "Variables" scope) is inherited by "child" components. I
am using it to good effect in a Unit Testing system that I work with.
Inheritance isn't always "evil" or useless - you should just make sure it is the best
solution for your problem rather than jumping into it without much thought. There are
some situations where it provides a very elegant solution over other options.
<cfcomponent name="Parent" >
<cfset Variables.Name = "I'm an object in a family" >
</cfcomponent>
<cfcomponent name="Child" extends="Parent" >
<cffunction name="GetName" >
<cfreturn Variables.Name > // returns "I'm an object in a family"
</cffunction>
</cfcomponent>
Jon
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