Re: [Rd] S4 setMethod, setGeneric and default arguments

From: Martin Morgan <mtmorgan_at_fhcrc.org>
Date: Mon, 22 Nov 2010 08:34:28 -0800

On 11/22/2010 03:23 AM, evilphil wrote:
>
> <BUMP>
>
> anyone?

Hi evilphil --

Your method signature doesn't have 'missing' for its third argument, and hence isn't the target of dispatch when the generic is invoked with a missing argument. I guess you'd figured that out and are really asking whether it's consistent with the S4 design, and I think it is.

Why one might provide a default to an argument that is also dispatched on seems like a design decision on your part. Maybe because missing argument dispatch is a common (default) use case? Or to advertise via the generic args what a typical value might be? But dispatch on multiple arguments becomes complicated -- the number of combinations of possible arguments is large, the 'next' method very difficult to reason about -- so might best be avoided if not necessary. The 'signature' argument of setGeneric allows arguments to be included but not dispatched on.

Martin

-- 
Computational Biology
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