I'm not sure what is meant by the original statement "The instance data
isn't inherited", but in the example shown below you need to run the init
method on the child in order for the instance variables to be created in it
because they are only created in the init method of the parent. Since you
are creating a new instance of Child, it won't know anything about your
instance of Parent in which it is being created.
If you change the line:
<cfset variables.theChild = createObject('component','Child')>
To
<cfset variables.theChild = createObject('component','Child').init()>
You will get what you want.
Why you would want to mix them in this way is another issue for another
thread.
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
> Behalf Of Nando
> Sent: Monday, December 08, 2003 8:30 AM
> To: [EMAIL PROTECTED]
> Subject: RE: [CFCDev] Difficulty in getting the light bulb to turn on...
>
>
> 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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