[R] R.oo Destructors

[Henrik Bengtsson]

Hi,

I'm about the head out of the office next 48 hours, but the short
answer is to override the finalize() method in your subclass of
Object.  This will be called when R garbage collects the object.  From
?finalize.Object:

 setConstructorS3("MyClass", function() {
    extend(Object(), "MyClass")
  })

  setMethodS3("finalize", "MyClass", function(this) {
    cat(as.character(this), "is about to be removed from the memory!\n")
  })

  o <- MyClass()
  o <- MyClass()
  o <- MyClass()
  o <- MyClass()
  gc()

  ## Not run:
MyClass: 0x31543776 is about to be removed from the memory!
MyClass: 0x31772572 is about to be removed from the memory!
MyClass: 0x32553244 is about to be removed from the memory!
         used (Mb) gc trigger (Mb) max used (Mb)
Ncells 246049  6.6     407500 10.9   350000  9.4
Vcells 132538  1.1     786432  6.0   404358  3.1

rm(o)
gc()

MyClass: 0x31424196 is about to be removed from the memory!
         used (Mb) gc trigger (Mb) max used (Mb)
Ncells 246782  6.6     467875 12.5   354145  9.5
Vcells 110362  0.9     786432  6.0   404358  3.1

Hope this helps

Henrik

On 1/18/07, Feng, Ken [CIB-EQTY] <ken.feng at citigroup.com> wrote:
>
> Has anyone figured out how to create a destructor in R.oo?
>
> How I'd like to use it:  I have an object which opens a connection thru RODBC
> (held as a private member) It would be nice if the connection closes automatically
> (inside the destructor) when an object gets gc()'ed.
>
> Thanks in advance.
>
> Regards,
> Ken
> BTW, a >BIG< thanks to Henrik Bengtsson for creating the R.oo package!
> Lucky for me as I am not smart enough to use S4...
>
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