From hpages at fhcrc.org  Thu Sep 27 03:01:19 2007
From: hpages at fhcrc.org (Herve Pages)
Date: Wed, 26 Sep 2007 18:01:19 -0700
Subject: [Rd] breaking my "length" method also breaks str()
Message-ID: <46FB00DF.9000903@fhcrc.org>

Hi,

This works fine and gives 26:

  setClass("A", representation(bidule="character"))
  setMethod("length", "A", function(x) length(x at bidule))
  a <- new("A", bidule=letters)
  str(a)
  length(a)

But if my "length" method is broken, then str() stops working:

  > setMethod("length", "A", function(x) length(x at bidulle))
  > str(a)
  Error in length(object) :
    no slot of name "bidulle" for this object of class "A"

Doesn't seem like a big deal on such a simple example but this can be
really problematic. I already had the situation where the "length" method
is in fact very complicated, with a lot of nested calls and one access to
a database and an error occurring at a deep level. I noticed that my program
had a problem but I was not yet aware that "length" was broken. So I started
the debug session and tried to use str() to look inside my objects... but
str() was not working! Which makes a debugging session with a lot of S4 stuff
all around the place quite painful :-/

Cheers,
H.



[Rd] breaking my "length" method also breaks str()
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