R help - Mar 2012 - Extending a group of S4 classes by setClassUnion ?

Hi,
I would like to create some S4 classes as follows

setClass("Father",representation(name="character"))
setClass("Son1",contains="Father",representation(par="numeric"))
setClass("Son2",contains="Father",representation(par="logical"))

Son1<-new("Son1")
Son1 at name<-"Son1"
Son1 at par<-3

Son2<-new("Son2")
Son2 at name<-"Son2"
Son2 at par<-TRUE

setGeneric("get.par",function(object){standardGeneric
("get.par")})
setMethod("get.par","Son1",function(object){return(object at
par+3)})
setMethod("get.par","Son2",function(object){return(!object
at par)})

get.par(Son1)
get.par(Son2)

So far, so good. I would like now, to create a new class, which
"extends"/"contains" the subclasses of Father by some
additional slots.
Is there any clean and simple possibility to inherite also the corresponding
function get.par ?

setClass("Extension",representation(person="Father",text="character"))
Ext<-new("Extension")
Ext at text<-"new try"
Ext at person<-Son1
get.par(Ext)
get.par(Ext at person)

Of course, "get.par(Ext)" returns an error. Is there any possibility
to tell
R, that if now function exists for a Class, to transform the object to a
class, for which the function exists ? (I know, it is not very clear what I
am writing, but I am doing my best). I don't want to rewrite every method
for  "Extension" like

setMethod("get.par","Extension",function(object){get.par(object
at person)})

Is there any simpler solution by steClassUnion, setAs, setIs .... ?

Thanks a lot in advance

Alexander

--
View this message in context:
http://r.789695.n4.nabble.com/Extending-a-group-of-S4-classes-by-setClassUnion-tp4475251p4475251.html
Sent from the R help mailing list archive at Nabble.com.

Hi Alexander --

On 03/15/2012 07:57 AM, Alexander wrote:
> Hi,
> I would like to create some S4 classes as follows
>
> setClass("Father",representation(name="character"))
>
setClass("Son1",contains="Father",representation(par="numeric"))
>
setClass("Son2",contains="Father",representation(par="logical"))
>
> Son1<-new("Son1")
> Son1 at name<-"Son1"
> Son1 at par<-3
it's more efficient to call new("Son1", name="Son1",
par=3)
> Son2<-new("Son2")
> Son2 at name<-"Son2"
> Son2 at par<-TRUE
>
> setGeneric("get.par",function(object){standardGeneric
("get.par")})
functions with '.' in their names can be confusing, because it could 
represent an S3 generic on 'get', for an S3 object of class
'par'.
>
setMethod("get.par","Son1",function(object){return(object at
par+3)})
>
setMethod("get.par","Son2",function(object){return(!object
at par)})
>
> get.par(Son1)
> get.par(Son2)
>
> So far, so good. I would like now, to create a new class, which
> "extends"/"contains" the subclasses of Father by some
additional slots.
> Is there any clean and simple possibility to inherite also the
corresponding
> function get.par ?
>
>
setClass("Extension",representation(person="Father",text="character"))
> Ext<-new("Extension")
> Ext at text<-"new try"
> Ext at person<-Son1
> get.par(Ext)
> get.par(Ext at person)
>
> Of course, "get.par(Ext)" returns an error. Is there any
possibility to tell
> R, that if now function exists for a Class, to transform the object to a
> class, for which the function exists ? (I know, it is not very clear what I
> am writing, but I am doing my best). I don't want to rewrite every
method
> for  "Extension" like
>
>
setMethod("get.par","Extension",function(object){get.par(object
at person)})
>
> Is there any simpler solution by steClassUnion, setAs, setIs .... ?
You can provide an explicit relationship

setIs("Extension", "Father",
       coerce=function(from) from at person,
       replace=function(from, value) {
           from at person <- value
           from
       })

and then define a method on 'Father' (since that's what you're
asserting
equivalence to)

setMethod("get.par", "Father", function(object) object at
name)

and finally have success with

ext <- new("Extension",
            person=new("Son1", name="Son1", par=3),
            text="new try")

 > get.par(ext)
[1] "Son1"

Neat, eh? But it really pays to ask whether the complexity of the class 
structure you're creating is appropriate for the solution that you need 
to implement -- imagine, for instance, writing a method that dispatches 
on two arguments, and as a programmer you need to implement appropriate 
methods for the tangle of dispatch that you have created.

Martin
>
> Thanks a lot in advance
>
> Alexander
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Extending-a-group-of-S4-classes-by-setClassUnion-tp4475251p4475251.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

-- 
Computational Biology
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N. PO Box 19024 Seattle, WA 98109

Location: M1-B861
Telephone: 206 667-2793