Strange behavior of assign in a S4 method.
Where did you get the idea that 'x' comes from the parent frame? There is no guarantee of this, and you are relying on/stumbling over implementation details here. (An extra call is inserted by setMethod() to handle the matching up of argumnets, but that is something which may change, and has changed in the history of the 'methods' package.) Note that 'x' might be an expression, even foo2(3, y=5). You need to check it is a symbol. It would seem to me to be much better to use a replacement function here (via setReplaceMethod in S4 land) and let the parser do most of the basic checking. Incidentally, at least in modern English, an assignation is (Collins English Dictionary) a secret or forbidden arrangement to meet and it seems rather that you _are_ trying to do something 'secret or forbidden'. (I suspect you mean 'assignment'.)
On Mon, 15 Mar 2010, Christophe Genolini wrote:
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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