I don't have anything to suggest on your specific example but perhaps
these two notes are relevant.
1. As is mentioned in the documentation, it's generally a bad idea to
write S4 initialize() methods for reference classes, rather than
reference class methods for $initialize():
"a reference method is recommended rather than a method for the S4
generic function initialize(), because some special initialization is
required for reference objects _before_ the initialization of fields."
2. In a simple example, there is no problem using .self in a
$initialize() method.
######
ss <- setRefClass("ss", fields = c("a", "b", "c"),
methods = list(
initialize = function(...) {
callSuper(...)
.self$b <- .self$a
},
check = function()
.self$c <- .self$a
))
s1 <- ss$new(a=1)
s1$check()
stopifnot(identical(s1$a, 1), identical(s1$a, s1$b),
identical(s1$a, s1$c))
#######
On 6/29/11 9:36 AM, Janko Thyson wrote:
Dear list,
I'm wondering if the following error I'm getting is a small bug in the
Reference Class paradigm or if it makes perfect sense.
When you write an explicit initialize method for a Ref Class, can you
then make use of '.self' WITHIN this initialize method just as you would
once an object of the class has actually been initialized?
Because it seems to me that you can not.
Below is an example that shows that calling '.self$someInitFoo()' within
the initialize method for 'MyClass' does not work (see section "METHODS"
in example below). Instead I have to go with
'someInitFooRefInner(.self=.Object, ...)' (see section "UPDATED METHOD"
in example below). Yet, this is only possible because there actually IS
such a method (I try to stick to the recommendations at ?setRefClass
where it says: "Reference methods should be kept simple; if they need to
do some specialized *R* computation, that computation should use a
separate *R* function that is called from the reference method")
The same problem occurs when, say 'someInitFoo()' calls yet another Ref
Class method (as is the case in the example below with a call to
'.self$someFoo()').
Is this a desired behavior?
Thanks for any clarifying comments!
Janko
##### CODE EXAMPLE #####
# CLASSES
setRefClass(
Class="MyVirtual",
contains=c("VIRTUAL"),
methods=list(
initialize=function(...){
callSuper(...)
return(.self)
},
someInitFoo=function(flds, ...){
someInitFooRefInner(
.self=.self,
flds=flds
)
}
)
)
GENERATOR<- setRefClass(
Class="MyClass",
contains=c("MyVirtual"),
fields=list(
A="character",
B="numeric"
),
methods=list(
someFoo=function(...){
someFooRefInner(.self=.self, ...)
}
)
)
# /
# GENERICS
setGeneric(name="someInitFooRefInner",
def=function(.self, ...) standardGeneric("someInitFooRefInner"),
signature=c(".self")
)
setGeneric(name="someFooRefInner",
def=function(.self, ...) standardGeneric("someFooRefInner"),
signature=c(".self")
)
# /
# METHODS
setMethod(
f="someInitFooRefInner",
signature=signature(.self="MyVirtual"),
definition=function(.self, flds, ...){
print("Trying to call '.self$someFoo()")
try(.self$someFoo())
print("Trying to call 'someFooRefInner(.self=.self)")
try(someFooRefInner(.self=.self))
return(flds)
}
)
setMethod(
f="someFooRefInner",
signature=signature(.self="MyVirtual"),
definition=function(.self, ...){
print("hello world!")
}
)
setMethod(
f="initialize",
signature=signature(.Object="MyVirtual"),
definition=function(.Object, GENERATOR=NULL, ...){
# MESSAGE
if(class(.Object) == "MyVirtual"){
cat(paste("initializing object of class '", class(.Object),
"'",
sep=""), sep="\n")
} else {
cat(paste("initializig object of class'", class(.Object),
"' inheriting from class 'MyVirtual'", sep=""), sep="\n")
}
# /
# GET GENERATOR OBJECT
if(is.null(GENERATOR)){
GENERATOR<- getRefClass(class(.Object))
}
flds<- names(GENERATOR$fields())
.Object$someInitFoo(
flds=flds,
...
)
return(.Object)
}
)
# /
x<- GENERATOR$new()
# UPDATED METHOD
setMethod(
f="initialize",
signature=signature(.Object="MyVirtual"),
definition=function(.Object, GENERATOR=NULL, ...){
# MESSAGE
if(class(.Object) == "MyVirtual"){
cat(paste("initializing object of class '", class(.Object),
"'",
sep=""), sep="\n")
} else {
cat(paste("initializig object of class'", class(.Object),
"' inheriting from class 'MyVirtual'", sep=""),
sep="\n")
}
# /
# GET GENERATOR OBJECT
if(is.null(GENERATOR)){
GENERATOR<- getRefClass(class(.Object))
}
flds<- names(GENERATOR$fields())
someInitFooRefInner(.self=.Object, flds=flds, ...)
return(.Object)
}
)
# /
x<- GENERATOR$new()
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