| callGeneric {methods} | R Documentation |
Call the Current Generic Function from a Method
Description
A call to callGeneric can only appear inside a method
definition. It then results in a call to the current generic
function. The value of that call is the value of callGeneric.
While it can be called from any method, it is useful and typically
used in methods for group generic functions.
Usage
callGeneric(...)
Arguments
... |
Optionally, the arguments to the function in its next call. If no arguments are included in the call to |
Details
The name and package of the current generic function is stored in the environment of the method definition object. This name is looked up and the corresponding function called.
The statement that passing no arguments to callGeneric causes
the generic function to be called with the current arguments is
more precisely as follows. Arguments that were missing in the current
call are still missing (remember that "missing" is a valid
class in a method signature). For a formal argument, say x, that
appears in the original call, there is a corresponding argument in the
generated call equivalent to x = x. In effect, this
means that the generic function sees the same actual arguments, but
arguments are evaluated only once.
Using callGeneric with no arguments is prone to creating
infinite recursion, unless one of the arguments in the signature has
been modified in the current method so that a different method is selected.
Value
The value returned by the new call.
References
Chambers, John M. (2016) Extending R, Chapman & Hall. (Chapters 9 and 10.)
Chambers, John M. (2008) Software for Data Analysis: Programming with R Springer. (Section 10.4 for some details.)
See Also
GroupGenericFunctions for other information
about group generic functions; Methods_Details for the general behavior
of method dispatch
Examples
## the method for group generic function Ops
## for signature( e1="structure", e2="vector")
function (e1, e2)
{
value <- callGeneric(e1@.Data, e2)
if (length(value) == length(e1)) {
e1@.Data <- value
e1
}
else value
}
## For more examples
## Not run:
showMethods("Ops", includeDefs = TRUE)
## End(Not run)