[Rd] Reference Classes: Generalizing Reference Class Generator objects?

[Jon Clayden]

Hi Daniel,

I think you want to define an "initialize" method, as in

TestClass <- setRefClass ("TestClass",
       fields = list (text = "character"),
       methods = list (
               initialize = function (text) { object <-
initFields(text=paste(text,"\n")) },
               print = function ()  { cat(text) } )
)

This seems to work as you intend:

> x <- TestClass$new("test")
> x$print()
test


All the best,
Jon

On 28 October 2010 15:13, Daniel Lee <bearlee at alum.mit.edu> wrote:
> Is it possible to override the $new(...) in the reference class generator? I
> have tried adding a "new" method to the methods of the class, but that is
> obviously not correct. I have also tried adding it to the class generator,
> but the class generator still uses the default constructor.
>
> As a simple example, this is the current interface:
> TestClass <- setRefClass ("TestClass",
>        fields = list (text = "character"),
>        methods = list (
>                print = function ()  {cat(text)})
> )
> test <- TestClass$new (text="Hello World")
> test$print()
>
> I would like to override $new(...) to be something like (add a "\n" to the
> end of the input, no need to specify input fields):
> TestClass$methods (new = function (text) {
>            text <- paste (text, "\n")
>            methods:::new (def, text=text)
>        })
>
> The constructor would then be:
> test <- TestClass$new ("Hello World")
>
> This is a subtle, but useful change. I have also tried adding to TestClass a
> method $newInstance(text), but that was not successful. If this is not
> possible, could we consider augmenting the Reference Class interface to
> include constructors?
>
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