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% File src/library/methods/man/MethodDefinition-class.Rd
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% Part of the R package, http://www.R-project.org
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% Copyright 1995-2007 R Core Team
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% Distributed under GPL 2 or later
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\name{MethodDefinition-class}
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\docType{class}
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\alias{MethodDefinition-class}
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\alias{SealedMethodDefinition-class}
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\title{Classes to Represent Method Definitions}
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\description{
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  These classes extend the basic class \code{"function"} when
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  functions are to be stored and used as method definitions.
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}
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\section{Objects from the Class}{
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  The action of setting a method by a call to \code{\link{setMethod}} creates an object of this class.  It's
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  unwise to create them directly.
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  The class \code{"SealedMethodDefinition"} is created by a call to
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  \code{\link{setMethod}} with argument \code{sealed = TRUE}.  It has
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  the same representation as \code{"MethodDefinition"}.
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}
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\section{Slots}{
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  \describe{
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    \item{\code{.Data}:}{Object of class \code{"function"}; the data
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        part of the definition. }
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    \item{\code{target}:}{Object of class \code{"signature"}; the
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        signature for which the method was wanted. }
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    \item{\code{defined}:}{Object of class \code{"signature"}; the
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        signature for which a method was found.  If the method was
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        inherited, this will not be identical to \code{target}. }
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      \item{\code{generic}:}{Object of class \code{"character"}; the function
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        for which the method was created. }
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  }
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}
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\section{Extends}{
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  Class \code{"function"}, from data part.\cr
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  Class \code{"PossibleMethod"}, directly.\cr
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  Class \code{"OptionalMethods"}, by class \code{"function"}.
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}
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\details{
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  Method definition objects are functions with additional information
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  defining how the function is being used as a method.  The
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  \code{target} slot is the class signature for which the method will
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  be dispatched, and the \code{defined} slot the signature for which
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  the method was originally specified (that is, the one that appeared
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  in some call to \code{\link{setMethod}}).
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}
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\seealso{class \code{\linkS4class{MethodsList}} for the objects
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  defining sets of methods associated with a particular generic
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  function.  The individual method definitions stored in these objects
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  are from class \code{MethodDefinition}, or an extension.
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  Class \code{\linkS4class{MethodWithNext}} for an extension used by
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  \code{\link{callNextMethod}}.
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}
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\keyword{classes}