R help - Jun 2011 - Question about R.oo package

Dear R.oo package users,

while testing some functionality of the R.oo, I found that during the first
construction of a object from a class, the constructor is twice called, but only
one object is finalized.

In all subsequent creation processes, the constructor is (expectedly) called
once.
Here some example code:

library(R.oo)
setConstructorS3("Test_class",function(val) {
				cat("constructor\n")
				if(missing(val)) val<-NA;
				extend(Object(), "Test_class", .val=val) })
setMethodS3("finalize","Test_class",function(this,...) {
cat("destructor\n") })
o<-Test_class(1)
rm(o)
gc()

Is there any explanation for this behaviour?

Thanks very much in advance

W. Kaisers

	[[alternative HTML version deleted]]

Hi W. Kaisers,

sorry for the delay - I just spotted you question:

On Thu, Jun 16, 2011 at 5:52 AM,  <Kaisers at med.uni-duesseldorf.de>
wrote:
> Dear R.oo package users,
>
> while testing some functionality of the R.oo, I found that during the first
construction of a object from a class, the constructor is twice called, but only
one object is finalized.
>
> In all subsequent creation processes, the constructor is (expectedly)
called once.
Yes, this is the expected behavior.  The reason is that the first time
the constructor is called, a static instance of the class is also
created (which is done by calling the constructor yet again without
arguments).  There is only one static instance of a class, so any
following calls to the constructor will not spawn a second call.

Related questions have been asked before and my answers then may
clarify this further, e.g.

[R] First call to constructor fails (R.oo), December 10, 2008
https://stat.ethz.ch/pipermail/r-help/2008-December/182212.html

[R] Help with R.oo, July 17, 2009
https://stat.ethz.ch/pipermail/r-help/2009-July/204951.html

Hope this helps

Henrik
> Here some example code:
>
> library(R.oo)
> setConstructorS3("Test_class",function(val) {
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?cat("constructor\n")
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?if(missing(val)) val<-NA;
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?extend(Object(), "Test_class",
.val=val) })
> setMethodS3("finalize","Test_class",function(this,...)
{ cat("destructor\n") })
> o<-Test_class(1)
> rm(o)
> gc()
>
> Is there any explanation for this behaviour?
>
> Thanks very much in advance
>
> W. Kaisers
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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