[Rcpp-devel] Designing Rcpp modules - allow access to fields or to field accessor methods?

[Douglas Bates]

My C++ coding style (such as it is) has been influenced by reading
Frank Bokken's "C++ Annotations".  I keep most data members of classes
private or protected and usually with names like d_x, d_y, d_weights,
etc. then provide accessor functions named x, y, weights, etc.
Generally the accessors return const references.

If I export such a class in an Rcpp module I can't allow field access
but can allow access from R to the accessor methods.  This seems
slightly awkward in that the user must know to use

myRefObj$x()

instead of

myRefObj$x

to access the x field.  Any strong opinions about fields access versus
access to field accessor methods?

As an example, one of my classes ends up looking like this

> getRefClass("Rcpp_lmResp")
Generator object for class "Rcpp_lmResp":

No fields defined

 Class Methods:
    "callSuper", "export", "finalize", "import", "initFields",
"initialize", "mu",
"offset", "sqrtrwt", "sqrtXwt", "updateMu", "updateWts", "wrss", "wtres", "y"


 Reference Superclasses:
    "envRefClass"

but all those methods except updateMu and updateWts are field accessors.

One advantage of this method is that one can't make changes to those
fields at the R level, which I like because I am paranoid about
introducing inconsistencies in the fields.