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Eclipse Platform
Release 3.5

org.eclipse.core.expressions
Interface IEvaluationContext

All Known Implementing Classes:
EvaluationContext

public interface IEvaluationContext

An evaluation context is used to manage a set of objects needed during XML expression evaluation. A context has a parent context, can manage a set of named variables and has a default variable. The default variable is used during XML expression evaluation if no explicit variable is referenced.

This interface is not intended to be implemented by clients. Clients are allowed to instantiate EvaluationContext.

Since:
3.0
Restriction:
This interface is not intended to be implemented by clients.
Restriction:
This interface is not intended to be extended by clients.

Field Summary
static  Object UNDEFINED_VARIABLE
          Represents the value used by variables that exist but are not defined in a evaluation context.
 
Method Summary
 void addVariable ( String name, Object value)
          Adds a new named variable to this context.
 boolean getAllowPluginActivation ()
          Returns whether this evaluation context supports plug-in activation.
  Object getDefaultVariable ()
          Returns the default variable.
  IEvaluationContext getParent ()
          Returns the parent context or null if this is the root of the evaluation context hierarchy.
  IEvaluationContext getRoot ()
          Returns the root evaluation context.
  Object getVariable ( String name)
          Returns the variable managed under the given name.
  Object removeVariable ( String name)
          Removes the variable managed under the given name from this evaluation context.
  Object resolveVariable ( String name, Object[] args)
          Resolves a variable for the given name and arguments.
 void setAllowPluginActivation (boolean value)
          Specifies whether this evaluation context allows activation of plug-ins for testers used in the expression tree.
 

Field Detail

UNDEFINED_VARIABLE

static final 
Object UNDEFINED_VARIABLE
Represents the value used by variables that exist but are not defined in a evaluation context. When tested by the 'with' expression, false will be returned.

Since:
3.4
Method Detail

getParent

IEvaluationContext getParent()
Returns the parent context or null if this is the root of the evaluation context hierarchy.

Returns:
the parent evaluation context or null

getRoot

IEvaluationContext getRoot()
Returns the root evaluation context.

Returns:
the root evaluation context

setAllowPluginActivation

void setAllowPluginActivation(boolean value)
Specifies whether this evaluation context allows activation of plug-ins for testers used in the expression tree. To actual trigger the plug-in loading this flag has to be set to true and the actual test expression must have the attribute forcePluginActivation set to true as well.

Parameters:
value - whether this evaluation context allows plug-in activation
Since:
3.2

getAllowPluginActivation

boolean getAllowPluginActivation()
Returns whether this evaluation context supports plug-in activation. If not set via setAllowPluginActivation(boolean) the parent value is returned. If no parent is set false is returned.

Returns:
whether plug-in activation is supported or not
Since:
3.2

getDefaultVariable

Object getDefaultVariable()
Returns the default variable.

Returns:
the default variable or null if no default variable is managed.

addVariable

void addVariable(
String name,
                 
Object value)
Adds a new named variable to this context. If a variable with the name already exists the new one overrides the existing one.

Parameters:
name - the variable's name
value - the variable's value

removeVariable

Object removeVariable(
String name)
Removes the variable managed under the given name from this evaluation context.

Parameters:
name - the variable's name
Returns:
the currently stored value or null if the variable doesn't exist

getVariable

Object getVariable(
String name)
Returns the variable managed under the given name.

Parameters:
name - the variable's name
Returns:
the variable's value or null if the content doesn't manage a variable with the given name

resolveVariable

Object resolveVariable(
String name,
                       
Object[] args)
                       throws 
CoreException
Resolves a variable for the given name and arguments. This method can be used to dynamically resolve variable such as plug-in descriptors, resources, etc. The method is used by the resolve expression.

Parameters:
name - the variable to resolve
args - an object array of arguments used to resolve the variable
Returns:
the variable's value or null if no variable can be resolved for the given name and arguments
Throws:
CoreException - if an errors occurs while resolving the variable

Eclipse Platform
Release 3.5

Guidelines for using Eclipse APIs.

Copyright (c) Eclipse contributors and others 2000, 2008. All rights reserved.


 
 
  Published under the terms of the Eclipse Public License Version 1.0 ("EPL") Design by Interspire