R help - Mar 2012 - Definition of generic function for subclasses

Hi,
I am working on a project, which contains S4 classes and subclasses. Lets
assume the following organisation:
A: S4 Class
B,C: inherit from A
D,E,F,G: inherit from B
H,I: inherit from C

I want to define now a generic function, which returns me the name of the
class. I can now write the function with "A" in the signature. Is
there any
reason to write the function for B,C, D,E,... with
"B","C","D","E", .. in
the signature ? I can imagine that it can become a mess if for example I
write a function for "A" and a special function for "I"
(lets assume, I is
the only exception).

Have you any best-work-pratice to share ?

Thanks
Alexander

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On 03/13/2012 04:34 AM, Alexander wrote:
> Hi,
> I am working on a project, which contains S4 classes and subclasses. Lets
> assume the following organisation:
> A: S4 Class
> B,C: inherit from A
> D,E,F,G: inherit from B
> H,I: inherit from C
>
> I want to define now a generic function, which returns me the name of the
> class. I can now write the function with "A" in the signature. Is
there any
?class for this function
> reason to write the function for B,C, D,E,... with
"B","C","D","E", .. in
> the signature ? I can imagine that it can become a mess if for example I
Implement the method at the lowest (highest?) level in the hierarchy as 
possible -- so on "A" only for the example of class.
> write a function for "A" and a special function for "I"
(lets assume, I is
> the only exception).
If 'I' is somehow special then write a method for it alone

   setClass("A"); setClass("C", "A");
setClass("I", "C")

   setGeneric("cls", function(x, ...)
standardGeneric("cls"))
   setMethod(cls, "A", function(x, ...) as.vector(class(x)))
   setMethod(cls, "I", function(x, ...) tolower(as.vector(class(x))))

and then

 > cls(new("C"))
[1] "C"
 > cls(new("I"))
[1] "i"
> Have you any best-work-pratice to share ?
Keep your class hierarchy simple and relevant to your actual problem.

Martin
>
> Thanks
> Alexander
>
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> View this message in context:
http://r.789695.n4.nabble.com/Definition-of-generic-function-for-subclasses-tp4468837p4468837.html
> Sent from the R help mailing list archive at Nabble.com.
>
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The definition of simple in "Keep your class hierarchy simple and relevant
to
your actual problem" is quite difficult. For someone who has programmed the
classes etc, it is quite simple to understand the heritance. But for example
for someone else, who has to maintain the code and the classes, it might
not.

I know how to define classes, and subclasses and generic function (and I
know also the helpfunction "?"). It is more about the concept. What is
the
best way to write good code which is easy to understand by others, easy to
maintain, but doesn't repeat the same generic function for every single
subclass... 

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