The function standardGeneric initiates dispatch of S4
  methods: see the references and the documentation of the
  methods package.  Usually, calls to this function are
  generated automatically and not explicitly by the programmer.
standardGeneric(f, fdef)The name of the generic.
The generic function definition. Never passed when defining a new generic.
standardGeneric dispatches the method defined for a generic
  function named f, using the actual arguments in the frame from which
  it is called.
The argument fdef is inserted (automatically) when dispatching
methods for a primitive function.  If present, it must always be the function
definition for the corresponding generic.  Don't insert this argument
by hand, as there is no validity checking and miss-specifying the
function definition will cause certain failure.
For more, use the methods package, and see the documentation in
  GenericFunctions.
Chambers, John M. (2008) Software for Data Analysis: Programming with R Springer. (For the R version.)
Chambers, John M. (1998) Programming with Data Springer (For the original S4 version.)