R help - Jul 2010 - class

Hello,
 
###  I created two classes "A" and "B". "A" is the
superclass of "B".
 
setClass("A",
representation(s1="numeric"),prototype=prototype(s1=8))
setClass("B",contains="A",representation(s2="character"),prototype=list(s2="hi"))
myA=new("A")
myB=new("B")
 
####  I created functions for "A" and "B"
 
f1=function(x,...) UseMethod("f")
f.default=function(x,...){
    print("default")
 }
 f.A=function(x,...) {
     print(paste("x@s1=", x@s1, sep=""))
     NextMethod()
 }
 f.B=function(x,...) {
     print(paste("x@s2=", x@s2, sep=""))
     NextMethod()
 }
 
#### when I do
 f1(myB)
## R gave me the result
[1] "x@s2=hi"
[1] "default"
## but I think the result should be 
[1] "x@s2=hi"
[1] "x@s1=8"
[1] "default"
 
## because the the NextMethod() should go to f1.A not directly to f1.default.
could you please tell me where I got wrong understanding?
 
Yu
 

 


      
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Hi, 

Strange, there seems to be different behavior of "old style" classes
and S4
classes.

This worked just like you expected (but it's not the same thing, no S4 
classes)

f2=function(x,...) UseMethod("fxy")
fxy.default=function(x,...){
	print("default")
}
fxy.X=function(x,...) {
	print("X")
	NextMethod()
}
fxy.Y=function(x,...) {
	print("Y")
	NextMethod()
}

x <- 1
y <- 2
class(x) <- c("X")
class(y) <- c("X", "Y")
f2(x)
f2(y)

Did you find a solution?

On Thursday 22 July 2010 10:23:37 am Yuan Jian wrote:
> Hello,
> ?
> ###? I created two classes "A" and "B". "A"
is the superclass of "B".
> ?
> setClass("A",
representation(s1="numeric"),prototype=prototype(s1=8))
>
setClass("B",contains="A",representation(s2="character"),prototype=list(s2>
"hi")) myA=new("A")
> myB=new("B")
> ?
> ####? I created functions for "A" and "B"
> ?
> f1=function(x,...) UseMethod("f")
> f.default=function(x,...){
> ??? print("default")
> ?}
> ?f.A=function(x,...) {
> ???? print(paste("x at s1=", x at s1, sep=""))
> ??? ?NextMethod()
> ?}
> ?f.B=function(x,...) {
> ??? ?print(paste("x at s2=", x at s2, sep=""))
> ???? NextMethod()
> ?}
> ?
> #### when I do
> ?f1(myB)
> ## R gave me the result
> [1] "x at s2=hi"
> [1] "default"
> ## but I think the result should be
> [1] "x at s2=hi"
> [1] "x at s1=8"
> [1] "default"
> ?
> ## because the the NextMethod() should go to f1.A not directly to
>  f1.default. could you please tell me where I got wrong understanding?
> ?
> Yu
> ?
> 
> ?
> 
> 
> 
> 	[[alternative HTML version deleted]]
> 
-- 
----
Friedrich Schuster
Dompfaffenweg 6
69123 Heidelberg