It makes no sense to replace the .self field: that field is initialized
to be a reference to the object. If you change it, it's no longer that
reference.
There are many things wrong with your example, so it's better to take a
very simple version:
> mkTest <- setRefClass("test",fields = list(a = "numeric"))
> x <- mkTest$new(a=1:10)
Now suppose we replace the .self field with another one:
> y <- mkTest$new(a = 11:20)
> x$.self <- y$.self
At this point x is messed up and does not correspond to the .self field:
> x$a
[1] 1 2 3 4 5 6 7 8 9 10
> x$.self$a
[1] 11 12 13 14 15 16 17 18 19 20
The same problem results no matter how you change the field. The only
difference with a method is that you do get a warning message.
> pseudoSelf <- as.environment(list(a = 5))
> x$.self <- pseudoSelf
> x$a
[1] 1 2 3 4 5 6 7 8 9 10
> x$.self$a
[1] 5
> mkTest$methods(screwup = function(newSelf) .self <<- newSelf)
Warning message:
In .checkFieldsInMethod(def, fieldNames, allMethods) :
Non-local assignment to non-field names (possibly misspelled?)
.self <<- newSelf
( in method "screwup" for class "test")
> x <- mkTest$new(a=1:10)
> x$screwup(pseudoSelf)
> x$a
[1] 1 2 3 4 5 6 7 8 9 10
> x$.self$a
[1] 5
We need to make the .self field read-only.
On 5/4/11 12:39 PM, Janko Thyson wrote:
Sorry guys,
but I chose a really stupid name before (no "reference classes").
Hope it's okay to re-post.
Cheers,
Janko
>>> ORIGINAL MESSAGE <<<
Dear list,
Is it possible to update or reassign '.self' with an image of '.self'
(e.g. a locally stored .Rda file) from within a method?
I know that this might sound akward, but here's the use case:
1) Ref Class Definition
setRefClass(Class="Test",
fields=list(A="character", B="character"),
methods=list(importImage=function(path){
variable <- load(path)
expr <- paste("assign('", variable, "',", variable, ", envir=.self)",
sep="")
eval(parse(text=expr))
}
)
2) Initialize Method Definition
setMethod(
f="initialize",
signature=signature(.Object="Test"),
definition=function(
.Object,
path=NULL
){
obj <- callNextMethod(.Object)
if(!is.null(path){
obj$importImage(path=path)
}
return(obj)
}
3) Intended and "Extended" Use
Method 'importImage' was originally intended to read either an object of
name 'A' or 'B' from a respective path and overwrite the respective
fields in an obj of class 'Test'.
Now I wondered how I could "reassign"/update the object of class 'Test'
itself by reading a respective .Rda image of an object of class 'Test'
from within 'obj$importImage()'.
The way I've written 'importImage()', it did not work. Yet I wonder if
it's possible.
4) My Workaround (but I'm looking for something more elegantly)
In the class definition:
[...]
methods=list(importImage=function(path){
variable <- load(path)
if(variable != ".self"){
expr <- paste("assign('", variable, "',", variable, ", envir=.self)",
sep="")
eval(parse(text=expr))
return(TRUE)
} else {
return(.self)
}
})
[...]
In the initialize method:
setMethod(
f="initialize",
signature=signature(.Object="Test"),
definition=function(
.Object,
path=NULL
){
obj <- callNextMethod(.Object)
if(!is.null(path){
rslt <- obj$importImage(path=path)
if(!is.logical(rslt)){
obj <- rslt
}
}
return(obj)
}
Thanks for any comments,
Janko
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