[R] Method for $

[Uwe Ligges]

Ulrike Grömping wrote:

> Dear R experts,
> 
> I have defined a class "myclass" and would like the slots to be extractable 
> not only by "@" but also by "$". I now try to write a method for "$" that 
> simply executes the request object at slotname, whenever someone calls 
> object$slotname for any object of class "myclass".
> I don't manage to find out how I can provide this function with "slotname", 
> so that one and the same function works for any arbitrary slotname a user 
> might choose.
> 
> I have tried
> 
> setMethod("$", signature(x="myclass"), function(x,slotname){ 
>  x at slotname 
>  } 
> )


Ulrike,

what about (untested!):
slot(x, slotname)

Best wishes from Dortmund and Lena,
Uwe Ligges


> This produced the error message: 
> In method for function "$": expanding the signature to 
> include omitted arguments in definition: name = "missing" 
> Error in rematchDefinition(definition, fdef, mnames, fnames, signature) : 
>         methods can add arguments to the generic only if '...' is an argument 
> to the generic
> 
> My searches for a solution of this problem have not been successful. Can 
> someone help? 
> 
> Thanks and regards,
> Ulrike Grömping, Berlin
> 
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