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% File src/library/methods/man/stdRefClass.Rd
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[% File src/library/methods/man/stdRefClass.Rd
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% Part of the R package, http://www.R-project.org
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% Part of the R package, http://www.R-project.org
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% Copyright 2010-2 R Core Team
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% Copyright 2010-2 R Core Team
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% Distributed under GPL 2 or later
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% Distributed under GPL 2 or later
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\name{envRefClass-class}
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\name{envRefClass-class}
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This class implements basic reference-style semantics for \R{}
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This class implements basic reference-style semantics for \R{}
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objects.  Objects normally do not come directly from this class, but
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objects.  Objects normally do not come directly from this class, but
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from subclasses defined by a call to \code{\link{setRefClass}}.
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from subclasses defined by a call to \code{\link{setRefClass}}.
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The documentation below is technical background describing the implementation, but applications
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The documentation below is technical background describing the implementation, but applications
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should use the interface documented under \code{\link{setRefClass}},
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should use the interface documented under \code{\link{setRefClass}},
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in particular the \code{\$} operator and field accessor functions as
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in particular the \code{$} operator and field accessor functions as
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described there.
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described there.
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}
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}
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\section{A Basic Reference Class}{
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\section{A Basic Reference Class}{
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The design of reference classes for \R{} divides those classes up
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The design of reference classes for \R{} divides those classes up
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and class methods.
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and class methods.
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Each version of this mechanism is defined by a \emph{basic reference
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Each version of this mechanism is defined by a \emph{basic reference
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  class}, which must implement a set of methods and provide some
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  class}, which must implement a set of methods and provide some
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further information used by \code{\link{setRefClass}}.
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further information used by \code{\link{setRefClass}}.
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The required methods are for operators \code{\$} and \code{\$<-} to
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The required methods are for operators \code{$} and \code{$<-} to
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get and set a field in an object, and for \code{\link{initialize}} to
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get and set a field in an object, and for \code{\link{initialize}} to
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initialize objects.
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initialize objects.
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To support these methods, the basic reference class needs to have some
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To support these methods, the basic reference class needs to have some
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implementation mechanism to store and retrieve data from fields in the
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implementation mechanism to store and retrieve data from fields in the
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objects.
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objects.
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Other basic reference classes may use an interface to a language such
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Other basic reference classes may use an interface to a language such
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as Java or C++ using reference semantics for classes.
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as Java or C++ using reference semantics for classes.
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Usually, the \R  user will be able to invoke class methods on the
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Usually, the \R  user will be able to invoke class methods on the
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class, using the \code{\$} operator.  The basic reference class
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class, using the \code{$} operator.  The basic reference class
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method for \code{\$} needs to make this possible.  Essentially, the
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method for \code{$} needs to make this possible.  Essentially, the
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operator must return an \R function corresponding to the object and
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operator must return an \R function corresponding to the object and
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the class method name.
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the class method name.
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Class methods may include an implementation of data abstraction, in
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Class methods may include an implementation of data abstraction, in
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the sense that fields are accessed by \dQuote{get} and \dQuote{set}
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the sense that fields are accessed by \dQuote{get} and \dQuote{set}