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\name{jfield}
\alias{.jfield}
\alias{.jfield<-}
\title{
Obtains the value of a field
}
\description{
\code{.jfield} returns the value of the specified field on an object.
}
\usage{
.jfield(o, sig = NULL, name, true.class = is.null(sig), convert = TRUE)
`.jfield<-`(o, name, value)
}
\arguments{
\item{o}{Class name or object (Java reference) whose field is to be
accessed. Static fields are supported both by specifying the class
name or using an instance.}
\item{sig}{signature (JNI type) of the field. If set to \code{NULL}
rJava attempts to determine the signature using reflection. For
efficiency it is recommended to specify the signature, because
the reflection lookup is quite expensive.}
\item{name}{name of the field to access}
\item{true.class}{by default the class of the resulting object matches
the signature of the field. Setting this flag to \code{TRUE} causes
\code{.jfield} to use true class name of the resulting object
instead. (this flag has no effect on scalar fields)}
\item{convert}{when set to \code{TRUE} all references are converted to
native types (where possible). Otherwise Java references are
returned directly.}
\item{value}{value to assign into the field. The field signature is
determined from the value in the same way that parameter signatures
are determined in \code{\link{.jcall}} - be sure to cast the value
as necessary, no automatic conversion is done.}
}
\value{
\code{.jfield}: contents of the field, \code{.jfield<-}: modified object.
}
\details{
The detection of a field signature in \code{.jfield} using reflection
is considerably expensive (more than 3 additional method calls have to
be performed), therefore it is recommended for time-critical code to
specify the field signature beforehand.
NOTE: The sequence of arguments in \code{.jfield} has been changed
since rJava 0.5 to be more consistent and match the sequence in
\code{.jcall}. Also \code{.jsimplify} is no longer needed as primitive
types are obtained directly.
}
\seealso{
\code{\link{.jcall}}
}
\examples{
\dontrun{
.jfield("java/lang/Boolean",, "TYPE")
}
}
\keyword{interface}
|
