R devel - Feb 2011 - Creating a reference class object from a class definition in a package fails

Hi,

I'm trying to create a package that contains reference class
definitions from which users can create reference objects, but there
seems to be something awry.

My toy example creates an empty package via
package.skeleton('TestClass') to which I add the following R code:

TestClass <- setRefClass('TestClass',fields=c('name'))

Unfortunately my R console output bears this:
> library(TestClass)
> TestClass$new(name='foo')
Error: attempt to apply non-function
> getRefClass('TestClass')$new(name='foo')
Error: attempt to apply non-function

Creating the same reference class in the global environment works though:
> x <- setRefClass('TestClass',fields='name')
> x$new(name='foo')
An object of class "TestClass"
<environment: 0x82a43cc>

I'm new to S4 and reference classes, so maybe I'm missing something
fundamental?

Jeff
> sessionInfo()
R version 2.13.0 Under development (unstable) (2011-02-02 r54197)
Platform: i686-pc-linux-gnu (32-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices datasets  utils     methods   base

other attached packages:
[1] TestClass_1.0

loaded via a namespace (and not attached):
[1] tools_2.13.0

Apparently reference classes must be declared in the NAMESPACE file
via an S4 declaration. If I place the following in the NAMESPACE file
all is well:

exportClasses(TestClass)
export(TestClass)


Jeff

On Wed, Feb 2, 2011 at 9:25 PM, Jeffrey Horner <jeffrey.horner at
gmail.com> wrote:
> Hi,
>
> I'm trying to create a package that contains reference class
> definitions from which users can create reference objects, but there
> seems to be something awry.
>
> My toy example creates an empty package via
> package.skeleton('TestClass') to which I add the following R code:
>
> TestClass <- setRefClass('TestClass',fields=c('name'))
>
> Unfortunately my R console output bears this:
>
>> library(TestClass)
>> TestClass$new(name='foo')
> Error: attempt to apply non-function
>> getRefClass('TestClass')$new(name='foo')
> Error: attempt to apply non-function
>
> Creating the same reference class in the global environment works though:
>
>> x <- setRefClass('TestClass',fields='name')
>> x$new(name='foo')
> An object of class "TestClass"
> <environment: 0x82a43cc>
>
> I'm new to S4 and reference classes, so maybe I'm missing something
fundamental?
>
> Jeff
>
>> sessionInfo()
> R version 2.13.0 Under development (unstable) (2011-02-02 r54197)
> Platform: i686-pc-linux-gnu (32-bit)
>
> locale:
> ?[1] LC_CTYPE=en_US.UTF-8 ? ? ? LC_NUMERIC=C
> ?[3] LC_TIME=en_US.UTF-8 ? ? ? ?LC_COLLATE=en_US.UTF-8
> ?[5] LC_MONETARY=C ? ? ? ? ? ? ?LC_MESSAGES=en_US.UTF-8
> ?[7] LC_PAPER=en_US.UTF-8 ? ? ? LC_NAME=C
> ?[9] LC_ADDRESS=C ? ? ? ? ? ? ? LC_TELEPHONE=C
> [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
>
> attached base packages:
> [1] stats ? ? graphics ?grDevices datasets ?utils ? ? methods ? base
>
> other attached packages:
> [1] TestClass_1.0
>
> loaded via a namespace (and not attached):
> [1] tools_2.13.0
>


-- 
http://biostat.mc.vanderbilt.edu/JeffreyHorner

You don't say, but my guess is you created the package without a namespace.

For reasons that are not too clear at the moment, the namespace seems to 
be needed.  At any rate, replicating your experiment with the argument 
namespace=TRUE to package.skeleton() worked:

 > require(TestClass2)
Loading required package: TestClass2
 > TestClass$new()
An object of class "TestClass"
<environment: 0x100df2e38>

Without that I replicated your result.

Namespaces are a good idea anyway, though other things being equal it 
would be nice not to require them.  For the moment, though, we do.

John


On 2/2/11 7:25 PM, Jeffrey Horner wrote:
> Hi,
>
> I'm trying to create a package that contains reference class
> definitions from which users can create reference objects, but there
> seems to be something awry.
>
> My toy example creates an empty package via
> package.skeleton('TestClass') to which I add the following R code:
>
> TestClass<- setRefClass('TestClass',fields=c('name'))
>
> Unfortunately my R console output bears this:
>
>> library(TestClass)
>> TestClass$new(name='foo')
> Error: attempt to apply non-function
>> getRefClass('TestClass')$new(name='foo')
> Error: attempt to apply non-function
>
> Creating the same reference class in the global environment works though:
>
>> x<- setRefClass('TestClass',fields='name')
>> x$new(name='foo')
> An object of class "TestClass"
> <environment: 0x82a43cc>
>
> I'm new to S4 and reference classes, so maybe I'm missing something
fundamental?
>
> Jeff
>
>> sessionInfo()
> R version 2.13.0 Under development (unstable) (2011-02-02 r54197)
> Platform: i686-pc-linux-gnu (32-bit)
>
> locale:
>   [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
>   [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
>   [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
>   [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
>   [9] LC_ADDRESS=C               LC_TELEPHONE=C
> [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
>
> attached base packages:
> [1] stats     graphics  grDevices datasets  utils     methods   base
>
> other attached packages:
> [1] TestClass_1.0
>
> loaded via a namespace (and not attached):
> [1] tools_2.13.0
>
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>