[Rd] Unexplained strange behaviour of callNextMethod in S4 methods

[Harold Petithomme]

Hello all.

A few days ago, I submitted a problem which remains unsolved although 
somebody answered to my question. I still have the problem. Can someone 
please explain if something is wrong ?

Have a look at this example:

setGeneric("f",valueClass="NULL",def=function(x) standardGeneric("f"))

setMethod("f",signature(x="A"),def=function(x)
{
    a = x at a
    cat("nombre :",a,"\n")
}
)

setMethod("f",signature(x="B"),def=function(x)
{
    cat("mot :",x at b,"\n")
    callNextMethod()
}
)

a = new("A",a=1)
b = new("B",b="hello",a)

f(a)
f(b)

This last command (f(b)) fails. But remove the 'valueClass="NULL"' 
setting in setGeneric or add argument x to the call to callNextMethod 
and it will be OK! Isn't it tricky?

Thanks in advance for any help.

Harold

-- 
*********************************************************
Harold PETITHOMME
Equipe Données et Outils de Prévision (DPREVI/COMPAS/DOP)

Météo France - Direction de la Production
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E-mail : harold.petithomme at meteo.fr