Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

68 lines (59 sloc) 2.446 kb
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2006-2011, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.util
import java.lang.InheritableThreadLocal
/** `DynamicVariables` provide a binding mechanism where the current
* value is found through dynamic scope, but where access to the
* variable itself is resolved through static scope.
*
* The current value can be retrieved with the value method. New values
* should be pushed using the `withValue` method. Values pushed via
* `withValue` only stay valid while the `withValue`'s second argument, a
* parameterless closure, executes. When the second argument finishes,
* the variable reverts to the previous value.
*
* {{{
* someDynamicVariable.withValue(newValue) {
* // ... code called in here that calls value ...
* // ... will be given back the newValue ...
* }
* }}}
*
* Each thread gets its own stack of bindings. When a
* new thread is created, the `DynamicVariable` gets a copy
* of the stack of bindings from the parent thread, and
* from then on the bindings for the new thread
* are independent of those for the original thread.
*
* @author Lex Spoon
* @version 1.1, 2007-5-21
*/
class DynamicVariable[T](init: T) {
private val tl = new InheritableThreadLocal[T] {
override def initialValue = init.asInstanceOf[T with AnyRef]
}
/** Retrieve the current value */
def value: T = tl.get.asInstanceOf[T]
/** Set the value of the variable while executing the specified
* thunk.
*
* @param newval The value to which to set the variable
* @param thunk The code to evaluate under the new setting
*/
def withValue[S](newval: T)(thunk: => S): S = {
val oldval = value
tl set newval
try thunk
finally tl set oldval
}
/** Change the currently bound value, discarding the old value.
* Usually withValue() gives better semantics.
*/
def value_=(newval: T) = tl set newval
override def toString: String = "DynamicVariable(" + value + ")"
}
Jump to Line
Something went wrong with that request. Please try again.