[Rd] Problem with initialize of S4 classes

[cstrato]

Dear Martin

Thank you for your comments!

You are correct, I have a name space but did not export "initialize",
since I thought that a user will never need to use it.

I will also try your suggestion to define a constructor in my package,
this seems to me to be a great idea.

Merry Christmas
Christian

Martin Morgan wrote:
> Hi Christian --
>
> Does your package have a name space, but not export 'initialize'?
> Calling 'new' will then go directly to the default constructors,
> generating the error. A different solution would be to define a
> constructor in your package
>
> PreFilter <- function(...) {
>     new("PreFilter", ...)
> }
>
> so that your user would not have to know about the details of calling
> new, you could provide helpful arguments to your constructor, and
> 'pre-processing' of arguments can be done (in the constructor) before
> calling 'new' (I find this helpful, to avoid have to be too careful
> when constructing initialize methods that deal with both the class and
> classes derived from the class).
>
> Martin
>
> cstrato <cstrato at aon.at> writes:
>
>   
>> Dear all
>>
>> Below is the code for "scriptPreFilter.R" which gives the following result:
>>  > source("scriptPreFilter.R")
>>  > prefltr <- new("PreFilter", mad=c(0.5,0.01))
>> [1] "------initialize:PreFilter------"
>> [1] "------initialize:Filter------"
>>  > str(prefltr)
>> Formal class 'PreFilter' [package ".GlobalEnv"] with 2 slots
>>   ..@ mad       :List of 2
>>   .. ..$ cutoff : num 0.5
>>   .. ..$ epsilon: num 0.01
>>   ..@ numfilters: num 1
>>
>> It seems that everything is ok, the results are as expected.
>>
>> However, my problem is that copying the identical code to my package 
>> results in an error:
>>  > prefltr <- new("PreFilter", mad=c(0.5,0.01))
>> [1] "------setValidity:Filter------"
>> Error in validObject(.Object) :
>>   invalid class "PreFilter" object: invalid object for slot "mad" in 
>> class "PreFilter": got class "numeric", should be or extend class "list"
>>
>> The following code avoids the error and gives the result:
>>  > prefltr <- new("PreFilter", mad=list(0.5,0.01))
>> [1] "------setValidity:Filter------"
>> [1] "------setValidity:PreFilter------"
>>  > str(prefltr)
>> Formal class 'PreFilter' [package "xps"] with 11 slots
>>   ..@ mad        :List of 2
>>   .. ..$ : num 0.5
>>   .. ..$ : num 0.01
>>   ..@ numfilters : num 0
>>
>> This is only partly correct, e.g. numfilters is 0.
>>
>> Only the following code gives the correct result:
>>  > prefltr <- new("PreFilter")
>>  > madFilter(prefltr) <- c(0.5,0.01)
>>  > str(prefltr)
>> Formal class 'PreFilter' [package "xps"] with 11 slots
>>   ..@ mad        :List of 2
>>   .. ..$ cutoff : num 0.5
>>   .. ..$ epsilon: num 0.01
>>   ..@ numfilters : num 1
>>
>> As you see, the loading "scriptPreFilter.R" calls method initialize but 
>> not setValidity.
>> In contrast, loading my package as library calls setValidity but not 
>> initialize.
>>
>> My question is:
>> - Why can the identical code behave differently when put in a package?
>> - How can I ensure, that initialize gets also called in my package?
>>
>>  > sessionInfo()
>> R version 2.6.1 (2007-11-26)
>> i386-apple-darwin8.10.1
>>
>> locale:
>> C
>>
>> attached base packages:
>> [1] stats     graphics  grDevices utils     datasets  methods   base     
>>
>> other attached packages:
>> [1] xps_0.4.0
>>
>> loaded via a namespace (and not attached):
>> [1] rcompgen_0.1-17
>>
>> Best regards and Merry Christmas
>> Christian
>> _._._._._._._._._._._._._._._._
>> C.h.i.s.t.i.a.n S.t.r.a.t.o.w.a
>> V.i.e.n.n.a       A.u.s.t.r.i.a
>> e.m.a.i.l:    cstrato at aon.at
>> _._._._._._._._._._._._._._._._
>>