[Rd] setOldClass("xts")

Hadley Wickham h.wickham at gmail.com
Wed Nov 4 15:00:57 CET 2015

Can you import the xts class from quantmod in your NAMESPACE?


On Wed, Nov 4, 2015 at 12:39 AM, Xavier Faure-Miller <xavier at 4ecap.com> wrote:
> Hello,
> I apologize that I am cross posting here after getting no answer from
> my initial
> question on stack overflow
> <http://stackoverflow.com/questions/33492601/r-setoldclass-only-if-needed>.
> I should certainly have posted it first here..
> I am using 3 packages:
>    - xts
>    - quantmod
>    - 'myPackage'
> quantmod is creating a union class by doing:
> setOldClass("xts");
> setClassUnion("xtsORzoo", c("xts","zoo"))
> In 'myPackage' I am also creating a union class by doing
> setOldClass("xts");
> setClassUnion("xtsOrNULL",members=c("xts", "NULL"))
> I did not notice any issue until: Since version 3.2.2
> <https://cran.r-project.org/doc/manuals/r-release/NEWS.html>, R is
> displaying a warning as soon as I manipulate an object of class xts:
> Found more than one class "xts" in cache; using the first, from
> namespace 'quantmod'Found more than one class "xts" in cache; using
> the first, from namespace 'quantmod'
> Indeed in this case it seems we are creating 2 virtual class for xts, one
> in package environement quantmod and one in package environment myPackage.
> Each is extended by different unionClass.
> 1) is it a problem (appart from this annoying warning?)
> 2) Should I instead use
> if (is.null(.Call(methods:::C_R_getClassFromCache, "xts",
> methods:::.classTable))) setOldClass("xts")
> So that I create the virtual class only of it has not been created by
> someone else in another package (and by the way in this case quantmod
> should do the same to avoid issues when packages are loaded in a different
> order)
> 3) and finally, is it not a bug in getClass ? I would have expected it to
> first try to get the class definition from the parent environment. The fact
> that I get the warning shows that it searches all environements, finds 2
> classes from 2 different environments and chooses arbitrarily.
> Thank you
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