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with and within methods for Java objects and class names

with.Rd

Convenience wrapper that allow calling methods of Java object and classes from within the object (or class).

Usage

# S3 method for class 'jobjRef'
with(data, expr, ...)
# S3 method for class 'jobjRef'
within(data, expr, ...)

# S3 method for class 'jarrayRef'
with(data, expr, ...)
# S3 method for class 'jarrayRef'
within(data, expr, ...)

# S3 method for class 'jclassName'
with(data, expr, ...)
# S3 method for class 'jclassName'
within(data, expr, ...)

Arguments

data

A Java object reference or a java class name. See J

expr

R expression to evaluate

...

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 makeActiveBinding) so that they can be accessed and modified from within the environment. For classes, only static fields are used.

Value

with returns the value of the expression and within returns the data argument

Author

Romain Francois <francoisromain@free.fr>

References

the java.lang.reflect package: https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/package-summary.html

Examples

#> Error in .jcheck(): java.lang.NoClassDefFoundError: RJavaArrayTools.jcall("java/lang/System", "S", "getProperty", "java.class.path")new("jobjRef", jobj = <pointer: 0x590bf6c97f02>, jclass = "java/lang/NoClassDefFoundError")

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 )
  } )
}
#> Error in .jcheck(): java.lang.NoClassDefFoundError: RJavaTools.jcall(x, target, get_method, object)new("jobjRef", jobj = <pointer: 0x590bf7fe1692>, jclass = "java/lang/NoClassDefFoundError")

Double <- J("java.lang.Double")
with( Double, MIN_VALUE )
#> Error in .jcall("RJavaTools", "[Ljava/lang/reflect/Field;", "getStaticFields",     clazz): RcallMethod: cannot determine object class
with( Double, parseDouble( "10.2" ) )
#> Error in .jcheck(): java.lang.NoClassDefFoundError: RJavaTools.jcall("RJavaTools", "[Ljava/lang/reflect/Field;", "getStaticFields", clazz)new("jobjRef", jobj = <pointer: 0x590bf7fe16a2>, jclass = "java/lang/NoClassDefFoundError")

if (FALSE) { # \dontrun{
# inner class example

HashMap <- J("java.util.HashMap")
with( HashMap, new( SimpleEntry, "key", "value" ) )
with( HashMap, SimpleEntry )
} # }

with( J("java.lang.System"), getProperty("java.home") )
#> Error in .jcall("RJavaTools", "[Ljava/lang/reflect/Field;", "getStaticFields",     clazz): RcallMethod: cannot determine object class

#> Error in .jcheck(): java.lang.NoClassDefFoundError: RJavaTools.jcall("RJavaTools", "[Ljava/lang/reflect/Field;", "getStaticFields", clazz)new("jobjRef", jobj = <pointer: 0x590bf7fe16b2>, jclass = "java/lang/NoClassDefFoundError")