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\alias{is}
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\alias{is}
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\alias{extends}
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\alias{extends}
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\alias{setIs}
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\alias{setIs}
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\title{Is an Object from a Class}
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\title{Is an Object from a Class}
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\description{
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\description{
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\code{is}:
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\code{is}:
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With two arguments, tests whether \code{object} can be treated as from
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With two arguments, tests whether \code{object} can be treated as from
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\code{class2}.
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\code{class2}.
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With one argument, returns all the super-classes of this object's class.
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With one argument, returns all the super-classes of this object's class.
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\code{extends}:
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\code{extends}:
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Does the first class extend the second class?
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Does the first class extend the second class?
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Returns \code{maybe} if the extension includes a test.
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Returns \code{maybe} if the extension includes a test.
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\code{setIs}:
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\code{setIs}:
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Defines \code{class1} to be an extension of \code{class2}.
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Defines \code{class1} to be an extension of \code{class2}.
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}
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}
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\usage{
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\usage{
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is(object, class2)
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is(object, class2)
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extends(class1, class2, maybe=TRUE, fullInfo = FALSE)
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extends(class1, class2, maybe=TRUE, fullInfo = FALSE)
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setIs(class1, class2, test=NULL, coerce=NULL, replace=NULL,
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setIs(class1, class2, test=NULL, coerce=NULL, replace=NULL,
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by = character(), where = topenv(parent.frame()), classDef =,
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by = NULL, where = 1, classDef, extensionObject, doComplete = TRUE)
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extensionObject = NULL, doComplete = TRUE)
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}
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}
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\arguments{
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\arguments{
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\item{object}{Any R object.}
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\item{object}{any \R object.}
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\item{class1, class2}{
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\item{class1, class2}{
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the names of the classes between which \code{is} relations are to be
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the names of the classes between which \code{is} relations are to be
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defined.}
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defined.}
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\item{maybe, fullInfo}{
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\item{maybe, fullInfo}{
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\dQuote{superclasses} of that class), including the class itself. If
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\dQuote{superclasses} of that class), including the class itself. If
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the flag \code{fullInfo} is \code{TRUE}, the result is a list, each
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the flag \code{fullInfo} is \code{TRUE}, the result is a list, each
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element of which is an object describing the relationship;
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element of which is an object describing the relationship;
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otherwise, and by default, the value returned is only the names of
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otherwise, and by default, the value returned is only the names of
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the classes.}
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the classes.}
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\item{\code{setIs}: }{
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\item{\code{setIs}: }{
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This function establishes an inheritance relation between two
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This function establishes an inheritance relation between two
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classes, by some means other than having one class contain the
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classes, by some means other than having one class contain the
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other. It should \emph{not} be used for ordinary relationships:
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other. It should \emph{not} be used for ordinary relationships:
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\code{coerce=} and \code{replace=} argument to \code{setIs}.
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\code{coerce=} and \code{replace=} argument to \code{setIs}.
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The \code{coerce}, \code{replace}, and \code{by} arguments behave as
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The \code{coerce}, \code{replace}, and \code{by} arguments behave as
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described for the \code{\link{setAs}} function. It's unlikely you
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described for the \code{\link{setAs}} function. It's unlikely you
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would use the \code{by} argument directly, but it is used in defining
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would use the \code{by} argument directly, but it is used in defining
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cached information about classes. The value returned (invisibly) by
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cached information about classes. The value returned (invisibly) by
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\code{setIs} is the extension information, as a list.
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\code{setIs} is the extension information, as a list.
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The \code{coerce} argument is a function that turns a
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The \code{coerce} argument is a function that turns a
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\code{class1} object into a \code{class2} object. The
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\code{class1} object into a \code{class2} object. The
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\code{class2} object by extracting the corresponding slots from the
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\code{class2} object by extracting the corresponding slots from the
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\code{class1} object. The \code{replace} function would replace in
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\code{class1} object. The \code{replace} function would replace in
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the \code{class1} object the slots corresponding to \code{class2},
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the \code{class1} object the slots corresponding to \code{class2},
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and return the modified object as its value.
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and return the modified object as its value.
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The relationship can also be conditional, if a function is supplied as the
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The relationship can also be conditional, if a function is supplied as the
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\code{test} argument. This should be a function of one argument
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\code{test} argument. This should be a function of one argument
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that returns \code{TRUE} or \code{FALSE} according to whether the
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that returns \code{TRUE} or \code{FALSE} according to whether the
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object supplied satisfies the relation \code{is(object, class2)}.
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object supplied satisfies the relation \code{is(object, class2)}.
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If you worry about such things, conditional relations between
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If you worry about such things, conditional relations between
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