On Tue, Sep 10, 2002 at 04:21:08PM +0200, demolombe
wrote:> Hello,
>
> I don't see how to add a method to a class.
> I can add "slots" (and retreive them by : myObject at slot1)
> but not methods, for example accessor for these slots
> and others functions.
You don't really add methods to a class. The system separates methods
from classes. On the method side, you first define a generic function
and then define some methods based on that.
A simple example (a queue class)
setClass("xQueue",
representation(env = "environment",
type = "character"))
##define a method for an existing generic
setMethod("initialize", "xQueue", function(.Object,
type="fifo") {
e1<-new.env(hash=TRUE)
assign("stack", vector("list", length=0), env=e1)
.Object at env=e1
.Object at type=type
.Object})
##define my own generic
setGeneric("push", function(object,value)
standardGeneric("push"))
##define my method
setMethod("push", signature(object="xQueue",
value="ANY"),
function(object, value ) {
st <- get("stack", env=object at env)
if (object at type=="fifo")
assign("stack", c(st, value), env=object at env)
else if (object at type=="lifo")
assign("stack", c(value, st), env=object at env)
return(invisible(value))
})
And, an example> x<-new("xQueue")
> x
An object of class "xQueue"
Slot "env":
<environment: 0x8d712c0>
Slot "type":
[1] "fifo"
> push(x, "10")
--writing pop is simple, but left for the reader
> Thanks for any help/tips
> Vincent
>
>
>
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