Message-ID: <3322A432-5855-4A70-ADC9-20AA39FB5B66@uni-bonn.de>
Date: 2013-07-23T16:59:15Z
From: Simon Zehnder
Subject: Check the class of an object
In-Reply-To: <21F05392-CB77-49C0-A35E-3989F8E99BFA@comcast.net>
Hi David,
thanks for the reply. You are right. Using the %in% is more stable and I gonna change my code.
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 <dwinsemius at 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
>>
>> [[alternative HTML version deleted]]
>
> Plain-text format is the recommended format for Rhelp
>
> --
> David Winsemius
> Alameda, CA, USA
>