Reference classes: accessor functions via 'getRefClass(...)$accessors(...)'

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Reference classes: accessor functions via 'getRefClass(...)$accessors(...)'

Janko Thyson
Hi there,

 

I'd like to choose between an "static" and "dynamic" access of a reference
class field, say 'a'.

 

myObj <- getRefClass("Blabla")$new()

 

Static:                   myObj$a

Dynamic:             myObj$a.get() where the function retrieves the data
from a database (or some other location), stores it to a buffer and
optionally updates the static field value 'a'.

 

I've set up such a method 'a.get()' where I can actually decide between
static and dynamic runmode (so the method also wraps the call 'myObj$a' for
the static runmode).

 

Now I saw that setting up such accessor methods (get/set) is already done
for me if I use 'getRefClass("Blabla")$accessors(.)'. I just don't
understand what exactly I have to do there, because this results in an
error: 'getRefClass("Blabla")$accessors("a")'

 

Can anyone point me to the correct use of 'getRefClass(.)$accessors(.)'?

 

Thanks a lot,

Janko


        [[alternative HTML version deleted]]

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Re: Reference classes: accessor functions via 'getRefClass(...)$accessors(...)'

Romain François-2
Le 17/11/10 13:07, Janko Thyson a écrit :

>
> Hi there,
>
>
>
> I'd like to choose between an "static" and "dynamic" access of a reference
> class field, say 'a'.
>
>
>
> myObj<- getRefClass("Blabla")$new()
>
>
>
> Static:                   myObj$a
>
> Dynamic:             myObj$a.get() where the function retrieves the data
> from a database (or some other location), stores it to a buffer and
> optionally updates the static field value 'a'.
>
>
>
> I've set up such a method 'a.get()' where I can actually decide between
> static and dynamic runmode (so the method also wraps the call 'myObj$a' for
> the static runmode).
>
>
>
> Now I saw that setting up such accessor methods (get/set) is already done
> for me if I use 'getRefClass("Blabla")$accessors(.)'. I just don't
> understand what exactly I have to do there, because this results in an
> error: 'getRefClass("Blabla")$accessors("a")'
>
>
>
> Can anyone point me to the correct use of 'getRefClass(.)$accessors(.)'?
>
>
>
> Thanks a lot,
>
> Janko

Hi,

fields can either be data or active binding functionss. See
?makeActiveBinding for some example of active binding functions in their
original context.

Here is an example of a reference class that keeps its data in a file.

require( methods )

Foo <- setRefClass( "Foo",
     fields = list(
         file = "character",
         x = function(value){
             if( missing( value ) ){
                 read.table( file )
             } else{
                 write.table( value, file = file )
             }
         }
     )
)

foo <- Foo$new( file="/tmp/iris.txt" )
foo$x <- iris
foo$x

write.table( subset( iris, Petal.Length < 2), file = "/tmp/iris.txt" )
foo$x


Does that help ?


Romain

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Re: Reference classes: accessor functions via 'getRefClass(...)$accessors(...)'

Vitalie S.-2
In reply to this post by Janko Thyson
"Janko Thyson" <[hidden email]> writes:

> Hi there,
>
> I'd like to choose between an "static" and "dynamic" access of a reference
> class field, say 'a'.
>
> myObj <- getRefClass("Blabla")$new()
>
> Static:                   myObj$a
>
> Dynamic:             myObj$a.get() where the function retrieves the data
> from a database (or some other location), stores it to a buffer and
> optionally updates the static field value 'a'.
>
> I've set up such a method 'a.get()' where I can actually decide between
> static and dynamic runmode (so the method also wraps the call 'myObj$a' for
> the static runmode).
>
> Now I saw that setting up such accessor methods (get/set) is already done
> for me if I use 'getRefClass("Blabla")$accessors(.)'. I just don't
> understand what exactly I have to do there, because this results in an
> error: 'getRefClass("Blabla")$accessors("a")'
>
> Can anyone point me to the correct use of 'getRefClass(.)$accessors(.)'?

It works for me:

X <- setRefClass("XXX", fields = list(a = "character"))
X$accessors("a")
X
# ...
# Class Methods:  
#    "callSuper", "export", "getA", "import", "initFields", "setA"
# ...

accessors() convenience method creates setA and getA functions:

x <- X$new()
x$getA
#Class method definition for method getA()
#function ()
#a
#<environment: 02a198c0>

HTH,
Vitalie.

>
>
> Thanks a lot,
>
> Janko
>
> [[alternative HTML version deleted]]

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Re: Reference classes: accessor functions via 'getRefClass(...)$accessors(...)'

Janko Thyson
Thanks a lot for the comments! I'll give the serveral alternatives a try to
see if it gets me what I want.

Cheers,
Janko

> -----Ursprüngliche Nachricht-----
> Von: Vitalie S. [mailto:[hidden email]]
> Gesendet: Mittwoch, 17. November 2010 13:51
> An: Janko Thyson
> Cc: 'r-devel@r-project. org'
> Betreff: Re: Reference classes: accessor functions via
> 'getRefClass(...)$accessors(...)'
>
> "Janko Thyson" <[hidden email]> writes:
>
> > Hi there,
> >
> > I'd like to choose between an "static" and "dynamic" access of a
> reference
> > class field, say 'a'.
> >
> > myObj <- getRefClass("Blabla")$new()
> >
> > Static:                   myObj$a
> >
> > Dynamic:             myObj$a.get() where the function retrieves the
> data
> > from a database (or some other location), stores it to a buffer and
> > optionally updates the static field value 'a'.
> >
> > I've set up such a method 'a.get()' where I can actually decide
> between
> > static and dynamic runmode (so the method also wraps the call
> 'myObj$a' for
> > the static runmode).
> >
> > Now I saw that setting up such accessor methods (get/set) is already
> done
> > for me if I use 'getRefClass("Blabla")$accessors(.)'. I just don't
> > understand what exactly I have to do there, because this results in
> an
> > error: 'getRefClass("Blabla")$accessors("a")'
> >
> > Can anyone point me to the correct use of
> 'getRefClass(.)$accessors(.)'?
>
> It works for me:
>
> X <- setRefClass("XXX", fields = list(a = "character"))
> X$accessors("a")
> X
> # ...
> # Class Methods:
> #    "callSuper", "export", "getA", "import", "initFields", "setA"
> # ...
>
> accessors() convenience method creates setA and getA functions:
>
> x <- X$new()
> x$getA
> #Class method definition for method getA()
> #function ()
> #a
> #<environment: 02a198c0>
>
> HTH,
> Vitalie.
>
> >
> >
> > Thanks a lot,
> >
> > Janko
> >
> > [[alternative HTML version deleted]]

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