The R Project SVN R

% File src/library/methods/man/getClass.Rd
% Part of the R package, http://www.R-project.org
% Copyright 1995-2007 R Core Development Team
% Distributed under GPL 2 or later

\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{\linkS4class{classRepresentation}}.  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{
 Chambers, John M. (2008)
 \emph{Software for Data Analysis: Programming with R}
  Springer.  (For the R version.)

 Chambers, John M. (1998)
 \emph{Programming with Data}
 Springer (For the original S4 version.)
}
\seealso{
  \link{Classes},
  \code{\link{setClass}},
  \code{\link{isClass}}.
}
\examples{
getClass("numeric") ## a built in class

cld <- getClass("thisIsAnUndefinedClass", .Force = TRUE)
cld ## a NULL prototype
## If you are really curious:
utils::str(cld)
## Whereas these generate errors:
try(getClass("thisIsAnUndefinedClass"))
try(getClassDef("thisIsAnUndefinedClass"))
}
\keyword{programming}
\keyword{classes}