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\name{with.jobjRef}
\alias{with.jobjRef}
\alias{within.jobjRef}
\alias{with.jarrayRef}
\alias{within.jarrayRef}
\alias{with.jclassName}
\alias{within.jclassName}
\title{
with and within methods for Java objects and class names
}
\description{
Convenience wrapper that allow calling methods of
Java object and classes from within the object (or class).
}
\usage{
\S3method{with}{jobjRef}(data, expr, ...)
\S3method{within}{jobjRef}(data, expr, ...)
\S3method{with}{jarrayRef}(data, expr, ...)
\S3method{within}{jarrayRef}(data, expr, ...)
\S3method{with}{jclassName}(data, expr, ...)
\S3method{within}{jclassName}(data, expr, ...)
}
\arguments{
\item{data}{
A Java object reference or a java class name. See \code{\link{J}}
}
\item{expr}{
R expression to evaluate
}
\item{\dots}{
ignored
}
}
\details{
The expression is evaluated in an environment
that contains a mapping between the public fields
and methods of the object.
The methods of the object are mapped to standard R functions
in the environment. In case of classes, only static methods
are used.
The fields of the object are mapped to active bindings
(see \link{makeActiveBinding}) so that they can be accessed
and modified from within the environment. For classes, only
static fields are used.
}
\value{
\code{with} returns the value of the expression and
\code{within} returns the \code{data} argument
}
\author{
Romain Francois <francoisromain@free.fr>
}
\references{
the \code{java.lang.reflect} package:
\url{https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/package-summary.html}
}
\examples{
\dontshow{.jinit()}
if (!nzchar(Sys.getenv("NOAWT"))) {
p <- .jnew( "java/awt/Point", 0L, 0L )
with( p, {
# x and y and now 0
move( 10L, 10L )
# x and y are now 10
x <- x + y
} )
f <- within( .jnew( "javax/swing/JFrame" ) , {
layout <- .jnew( "java/awt/BorderLayout" )
setLayout( layout )
add( .jnew( "javax/swing/JLabel", "north" ), layout$NORTH )
add( .jnew( "javax/swing/JLabel", "south" ), layout$SOUTH )
add( .jnew( "javax/swing/JLabel", "west" ), layout$WEST )
add( .jnew( "javax/swing/JLabel", "east" ), layout$EAST )
setSize( .jnew( "java/awt/Dimension", 400L, 400L ) )
setVisible( TRUE )
} )
}
Double <- J("java.lang.Double")
with( Double, MIN_VALUE )
with( Double, parseDouble( "10.2" ) )
\dontrun{
# inner class example
% TODO: find a better example
HashMap <- J("java.util.HashMap")
with( HashMap, new( SimpleEntry, "key", "value" ) )
with( HashMap, SimpleEntry )
}
with( J("java.lang.System"), getProperty("java.home") )
\dontshow{
stopifnot( with( Double, parseDouble("10.0") ) == 10.0 )
d <- new( Double, "10.0")
stopifnot( with( d, doubleValue() ) == 10.0 )
}
}
\keyword{ classes }
|
