The R Project SVN R

\name{getClass}

\alias{getClass}

\alias{getClassDef}

\title{Get Class Definition }

\description{

  Get the definition of a class.

}

\usage{

getClass(Class, .Force = FALSE, where)

getClassDef(Class, where, package)

}

\arguments{

  \item{Class}{ the character-string name of the class.}

  \item{.Force}{ if \code{TRUE}, return \code{NULL} if the class is

    undefined; otherwise, an undefined class results in an error.}

  \item{where}{ environment from which to begin the search for the definition; by default,

    start at the top-level (global) environment and proceed through

    the search list.}

  \item{package}{ the name of the package asserted to hold the

      definition.  Supplied instead of \code{where}, with the

      distinction that the package need not be currently attached.}

}

\details{

  A call to \code{getClass} returns the complete definition of the class

  supplied as a string, including all slots, etc. in classes that this

  class extends.  A call to \code{getClassDef} returns the definition of

  the class from the environment \code{where}, unadorned.  It's usually \code{getClass}

  you want.

  If you really want to know whether a class is formally

  defined, call \code{\link{isClass}}.

}

\value{

  The object defining the class.  This is an object of class

  \code{"classRepEnvironment"}.  However, \emph{do not} deal with the

  contents of the object directly unless you are very sure you know what

  you're doing.  Even then, it is nearly always better practice to use

  functions such as \code{\link{setClass}} and \code{\link{setIs}}.

  Messing up a class object will cause great confusion.

}

\references{

  The R package \pkg{methods} implements, with a few exceptions, the

  programming interface for classes and methods in the book

  \emph{Programming with Data} (John M. Chambers, Springer, 1998), in

  particular sections 1.6, 2.7, 2.8, and chapters 7 and 8.

  While the programming interface for the methods package follows the

  reference, the R software is an original implementation, so details in

  the reference that reflect the S4 implementation may appear

  differently in R.  Also, there are extensions to the programming

  interface developed more recently than the reference.  For a

  discussion of details and ongoing development, see the web page 

  \url{http://developer.r-project.org/methodsPackage.html} and the

  pointers from that page.

}

\seealso{

  \link{Classes},

  \code{\link{setClass}},

  \code{\link{isClass}}.

}

\examples{

getClass("numeric") ## a built in class

\dontshow{

getClass("thisIsAnUndefinedClass", .Force = TRUE) ## returns NULL

try(getClass("thisIsAnUndefinedClass")) ## generates an error

try(getClassDef("thisIsAnUndefinedClass")) ## generates an error

}

}

\keyword{programming}

\keyword{classes}