On 02/02/2010 02:12 PM, bull...@stat.berkeley.edu wrote:
>
> Hi, I recently ran into this problem. I couldn't find any mention of it in
> the setClass documentation.
>
> setClass("Foo", representation(file = "character"))
> setMethod("initialize", "Foo", function(.Object, file) {
> print(file)
> })
> setClass("Bar", contains = "Foo")
>
> And the error:
>
> Error in print(file) : argument "file" is missing, with no default
>
> The workaround is to interchange the setMethod and the second setClass
> call, however, it begs the question why is setClass calling an initialize
> method? As always, if I have missed documentation concerning this please
> point me there.
Hi Jim -- The hint is in traceback()
> setClass("Bar", contains="Foo")
Error in print(file) : argument "file" is missing, with no default
> traceback()
[snip]
5: new(toDef)
4: .simpleCoerceExpr(Class, to, names(slots), classDef2)
3: makeExtends(name, what, slots = slots, classDef2 = whatClassDef,
package = package)
2: makeClassRepresentation(Class, properties, superClasses, prototype,
package, validity, access, version, sealed, where = where)
1: setClass("Bar", contains = "Foo")
the source
if(!isVirtualClass(toDef))
toClass <- class(new(toDef)) # get it with the package slot correct
subversion
% svn annotate src/library/methods/R/RClassUtils.R
48221 jmc if(!isVirtualClass(toDef))
48221 jmc toClass <- class(new(toDef)) # get it with
% svn log -r 48221
------------------------------------------------------------------------
r48221 | jmc | 2009-03-26 14:28:03 -0700 (Thu, 26 Mar 2009) | 1 line
fix bug in defining as() methods--got wrong package for simple contains
class with no added slots
------------------------------------------------------------------------
and the mailing list
https://stat.ethz.ch/pipermail/r-devel/2009-March/052829.html
but the bottom line is that you want
validObject(new("Foo"))
to return TRUE. I'd write (if an initialize method is really required --
what happens if there's a constructor Foo() that constructs the
arguments to new("Foo", <...>) correctlyl?)
setMethod(initialize, function(.Object, ..., file=character(0)) {
## process file, then
callNextMethod(.Object, ..., file=file)
})
'file' gets a default argument. '...' allows derived classes to
callNextMethod (explicitly, or implicitly by a call to new("Bar",
<...>)) and get the expected 'initialize' behavior. Placing 'file' after
'...' means that 'file' doesn't capture unnamed arguments, which are
supposed to be prototypes for classes that .Object extends.
Martin
>
> Thanks, jim
>
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--
Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N.
PO Box 19024 Seattle, WA 98109
Location: Arnold Building M1 B861
Phone: (206) 667-2793
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