Draft of a help function for method documentation similar to reference classes

[paulstaab]

Related to #2, I was looking for ways to document methods. The code in this pull request mimics the documentation system of reference classes, where each methods can optionally be documented with a string, given as first line of its body:

TC <- R6Class("test_class",
              public = list(getx = function() { 'Gets x'; private$x },
                            setx = function(x) { 'Sets x'; self$x <- x },
                            one = function() 1,
                            help = R6_help),
              private = list(x = 1)
)
T <- TC$new()
T$help('setx')
# test_class$setx: Sets x
T$help('getx')
# test_class$getx: Gets x
T$help('one')
# test_class$one: No documentation available.

The help function could be automatically added to all objects. Would you be interested in including something like this in R6? If there is interest on your side, I will happily improve the code until it is fit for being included.

[wch]

Hm, I'm not sure yet that this is the way to go. I do like that it's optional, and that the class author would have to explicitly opt-in. It would be nice if T$help() listed all the methods, and possibly public fields.

I'm leaning toward making it easier to create real .Rd documentation, though. @hadley tells me that, for reference classes, roxygen2 has support for pulling out doc strings and putting them into man pages. It would need some tweaking to work with R6, though.

[paulstaab]

Yes, real .Rd documentation is definitely better. Guess the user would than call something like ?test_class$setx to view the page?

[paulstaab]

Documentation as in suggested in #3 works for me. I'm closing this PR.