Hi,
On 07/23/2013 09:59 AM, Simon Zehnder wrote:
Hi David,
thanks for the reply. You are right. Using the %in% is more stable and I gonna
change my code.
Unlike with S3 objects, class() on an S4 object can only return 1 class.
Also note that, on an S3 object, doing
"firstClass" %in% class(myObject)
is equivalent to doing inherits(myObject, "firstClass"), which is
what you said you wanted to avoid. The most specific class should be
the first so if that's what you wanted to check, you could do
class(myObject)[1] == "firstClass"
But that precaution is not needed if 'myObject' is guaranteed to be
an S4 object (although when writing a unit test, one should probably
discard any guarantee of that sort).
Cheers,
H.
When testing for a specific class using 'is' one has to start at the lowest
heir and walk up the inheritance structure. Starting at the checks at the root
will always give TRUE. Having a structure which is quite complicated let me
move to the check I suggested in my first mail.
Best
Simon
On Jul 23, 2013, at 6:15 PM, David Winsemius <dwinsem...@comcast.net> wrote:
On Jul 23, 2013, at 5:36 AM, Simon Zehnder wrote:
Dear R-Users and R-Devels,
I have large project based on S4 classes. While writing my unit tests I found
out, that 'is' cannot test for a specific class, as also inherited classes can
be treated as their super classes. I need to do checks for specific classes.
What I do right now is sth. like
if (class(myClass) == "firstClass") {
I would think that you would need to use `%in%` instead.
if( "firstClass" %in% class(myObject) ){
Objects can have more than one class, so testing with "==" would fail in those
instances.
} else if (class(myClass) == "secondClass") {
}
Is this the usual way how classes are checked in R?
Well, `inherits` IS the usual way.
I was expecting some specific method (and 'inherits' or 'extends' is not what I
look for)...
Best
Simon
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David Winsemius
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