[Bioc-devel] R6 and Bioconductor

[Gabe Becker]

On May 12, 2017 4:23 PM, "Garth Ilsley" <garth.ilsley at oist.jp> wrote:

Thank you.

> One place where one might think of using R6 is in the implementation of a
mutable data model underlying a GUI like a Shiny app. > If mutable
semantics are required, consider using S4 reference classes, as they offer
more features than R6 and will integrate
> directly with Bioconductor S4 classes.

If I understand correctly, you are saying that it is fine to use Reference
classes (mutable semantics) in Bioconductor. A GUI is one clear place for
this. However, what about a large dataset that is subject to progressive
analysis with various fields updated as the analysis proceeds? The typical
Bioconductor approach (as far as I have seen) is to call a method defined
for an S4 functional class that produces a new object of the same class,
with the result assigned to the same name as the original object.  For a
project considered in isolation, it wouldn't be unreasonable to use a
Reference class for this instead, but that's not what I'm asking. My
question is about the standards and approach that Bioconductor has agreed
on - to ensure consistency. Is a Reference Class permissible in this
situation?


I dont speak for the project, but i would suggest that reference classes
are really best/(almost) only useful for encoding state in
complex/unusual-for-r package code. Having user-facing objects with these
mechanics violates a pretty central idiom of R (copy on write) and thus is
imo substantially more damaging than it is worth in general.

One of the things that makes r simpler for beginners than other languages
is that when they pass an object to a function that function "can't" change
the version they have in their workspace.

If not, case closed. If they are permitted, I would suggest that R6
semantics are consistent with Reference Class semantics, but with the added
benefit of private members and "active bindi
 ngs" (they look like fields, but call a function).


Refence classes absolutely can have active binding fields. It is pretty
standard practice I think.

As for private fields, no they don't have that, but I've never really been
convinced you need them in the vast vast majority of cases. R is designed
such that the user owns their data (ie the contents of their objects). I've
never really heard a good augment why that shouldn't be the case.

That said the typical idiom in all of my code is to have paired fields, an
active binding which is a function. That does some checking/processing and
a classed field with the same name prepended with a . That it corresponds
to.

Also R6 aren't really compatible with reference class/S4 mechanics because
the fields are not classed. This may sound like a small thing but imo it's
actually quite important.

Best,
~G


This is nice and simple (for the creator and user of the class), but if not
desired (for consistency etc.), then I presume Reference Classes will do
fine.


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