[R] Changing the value of an object's slot in a method

[tofesi@web.de]

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Hi all,

I want to modify the value of an object's slot from within a method, as in the example below:

setClass("MyClass", representation(flag="numeric"))
if( !isGeneric("flipFlag") )
    setGeneric("flipFlag", function(object)
               standardGeneric("flipFlag"))
setMethod("flipFlag","MyClass",
          function(object) {

            # flips object at flag from 0 to 1, or from 1 to 0
          })

This should work in a similar way as in other object-oriented languages where it would be written as 'object.flipFlag()'. However, there seems to be a problem with the call-by-value semantics of R, and the updated value is lost on leaving the function.

The following two options are not suitable for our task:
1.) Directly assigning to 'flag' via a method created by 'setReplaceMethod'. The method 'flipFlag' should require no parameters.
2.) Returning a new object, so that the user has to assign the new object to the old variable.

Thanks in advance,
  Tobi.
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