Hi,
I think your issue is that in the absence of an explicit 'initialize' method
the value of id is assigned when you define the class prototype. All
subsequent new instances will use that very same prototype value defined when
you first defined the class. That's in the help for ?new, "The function new
begins by copying the prototype object from the class definition." Read on in
the details section to learn more about 'initialize'.
To get a new id for each new object instance you can define an 'initialize'
method.
setMethod("initialize",
"C",
function(.Object){
.Object@id = UUIDgenerate(use.time = TRUE)
.Object
})
> new("C")
An object of class "C"
Slot "id":
[1] "f5e87504-2d83-11e6-9dcb-685b35bcefe9"
> new("C")
An object of class "C"
Slot "id":
[1] "f73cf010-2d83-11e6-9dcb-685b35bcefe9"
> new("C")
An object of class "C"
Slot "id":
[1] "f8321f22-2d83-11e6-9dcb-685b35bcefe9"
> new("C")
An object of class "C"
Slot "id":
[1] "f96e3c90-2d83-11e6-9dcb-685b35bcefe9"
There may be other ways to achieve the same outcome. Caveat... I handy with
Reference Classes (see ?setRefClass) but have only recently exploring S4
classes.
Cheers,
Ben
> On Jun 8, 2016, at 8:24 AM, Servet Ahmet Çizmeli
> <servet.ahmet.cizm...@usherbrooke.ca> wrote:
>
>
>
> Hello
>
> When I create a new instance of an S4 class in R, I would like the newly
> created object to have a unique id field. I try to achieve it through
> UUIDgenerate() from the uuid package. The problem is that I obtain the
> same UUID at every new object instance :
>
> library(uuid)
> setClass("C",
> representation=representation(
> id = "character"
> ),
> prototype = prototype(
> id = UUIDgenerate(use.time = TRUE))
> )
>
> new("C")
>
> An object of class "C" Slot "id": [1]
> "1e07d7c2-2d71-11e6-b5e1-e1f59d8ccf09"
>
> new("C")
>
> An object of class "C" Slot "id": [1]
> "1e07d7c2-2d71-11e6-b5e1-e1f59d8ccf09"
>
> new("C")
>
> An object of class "C" Slot "id": [1]
> "1e07d7c2-2d71-11e6-b5e1-e1f59d8ccf09"
>
> Calling UUIDgenerate() successively at the R command line produces
> different UUIDS each time.
>
> Where do I go wrong?
>
> Thanks
>
> Servet
>
>
> [[alternative HTML version deleted]]
>
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Ben Tupper
Bigelow Laboratory for Ocean Sciences
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______________________________________________
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