R help - Jul 2013 - Check the class of an object

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") {

} else if (class(myClass) == "secondClass") {

}

Is this the usual way how classes are checked in R? I was expecting some
specific method (and 'inherits' or 'extends' is not what I look
for)...


Best

Simon





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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]]
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David Winsemius
Alameda, CA, USA