Re: [Rd] Strange behavior of assign in a S4 method.

[Christophe Genolini]

Dear Wolfgang,

Thanks for the showMethod and the link.

Perhaps juggling with the 'n' argument of 'parent.frame' could help in 
hacking something together that 'works'
I just change the argument list of foo2 to perfectly match with the 
definition.
but as far as I can see what you want to is an abuse of R's pass by 
value / functional language semantics.

Yes I kown. When I learnt object programming, one of the basic was that 
some methods was design to change internals value of the fields. It is 
what I try to do here.
For example, try these and check whether this results in what you 
intended:

foo2(3)
foo2(e+2)
sapply(1:5, foo2)
ls()
This will not apply, because I my case, the function foo2 is avalable 
only for object of class FooClass and the only possible use will be :

toto <- new("FooClass")
....
foo2(toto)

Best wishes
Christophe

    Best wishes
    Wolfgang


Christophe Genolini scripsit 15/03/10 11:33:
Hi the list,
I define a method that want to change an object without assignation 
(foo(x) and not x<-foo(x)) using deparse and assign.
But when the argument of the method does not match *exactly* with the 
definition of the generic function, assign does not work...
Anything wrong?

Christophe

#------ Does not work ------#
setGeneric("foo1",function(x,...){standardGeneric("foo1")})

setMethod(f="foo1",signature="numeric",definition=
   function(x,y=1,...){
       nameX<-deparse(substitute(x))
       x <- x^2
       assign(nameX,x,envir=parent.frame())
   }
)

e <- 3
foo1(e,y=5)
cat(e)


#------ Does work ------#
setGeneric("foo2",function(x,...){standardGeneric("foo2")})

setMethod(f="foo2",signature="numeric",definition=
   function(x,...){
       nameX<-deparse(substitute(x))
       x <- x^2
       assign(nameX,x,envir=parent.frame())
   }
)

e <- 3
foo2(e,y=5)
cat(e)

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Wolfgang Huber
EMBL
http://www.embl.de/research/units/genome_biology/huber/contact




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