Eclipse Core Expression Usage

Http://codeandme.blogspot.com/2012/04/expression-examples.html

We need to set checkenabled in the visiblewhen element to false, otherwise the expression would Not is active. The withsection uses Activepartid as source. It is a string containing the ID of the active view/editor (see description).

Http://wiki.eclipse.org/Command_Core_Expressions#Variables_and_the_Command_Framework

Core expressions is declarative or programmatic expressions based on the Org.eclipse.core.expressions plugin. Through Org.eclipse.core.expression to achieve

The Platform Command Framework uses core expressions for Enabledwhen and activewhen for handlers, programmatic activation of contexts, and for Visiblewhen for menu contributions. The command framework provides the IEVALUATIONCONTEXT that command core expressions is evaluate against.

The Ievaluationcontext provides a default variable for evaluations, and a number of named variables. In the command framework, we provide the global selection as a as the java.util.Collection default variable. It can either be empty, having one entry (if the iselection is something like an itextselection), or having the contents of a N Istructuredselection.

The <with/> element can be used to change which variable, the child expression elements is evaluating against.

The command in Eclipse plugin introduces the core expressions to activate the corresponding command

Enabledwhen,activewhen is used for handler;

Visiblewhen for menu Menus

re-usable expressions

Sometimes you'll end up with have the same expression in many different places. When one of the them changes, you had to change them all. Obviously, this is inefficient and not very handy-let alone error prone. You can get around this problem by using the definitions and re-use expressions that is declared elsewhere.

The expression from the example above can is declared using org.eclipse.core.expressions.definitions the extension point, and then re-used using the <reference> ele ment:

Reusing an expression

Http://wiki.eclipse.org/Platform_Expression_Framework

• Should an context menu is enabled and/or visible in a context menu menu should not be displayed or is available
• Which implementation for a command handler to using depending on the current context which handler should be used
• Which label provider to using for a object which provider should be used
• Which content provider can provide children for an object in a tree

<or>element contains an expression block

Expression BLOCK:

instanceof:

Adapt

<reference          definitionid= "org.acme.navigator.enablement" >    </reference>

Usually, expressions check the default variable in the evaluation context. However, it is possible for an expression to select a specific variable from the context using the <with> element (examples below).

It is common to check the default variables, but you can use the with to check the variables.

When dealing with a collection, we usually want to know what's in this collection.

It's used here <iterate> <count>

They require an Iterable object to work (otherwise they fail with a error message on the console) they must be an iterative object.

The default variable is currently selected, but may be the entire structure.

ITextSelection), or contain the elements of an IStructuredSelection .

Adapt,and,or,not can contain internal elements.

Count cannot contain elements, he is the number of elements in the calculation collection.

It is best to work with <iterate> to traverse the number of all elements inside.

<count value= "2"/>

<iterate ifempty= "false" >

<instance of value= ""/>

</iterate>

Resolve will not be used again.

As of Eclipse 3.5, there is no implementation in either the command framework or the Common Navigator framework for Ivaria Bleresolver, so the operator is a use for <resolve> them.

Systemtest

Property values in the test system

Java.lang.System.getProperties

With

A variable will be defined for validation. Child elements must be used. A variable that can make a system.

For example, the currently active window, and so on.

Eclipse Core Expression Usage