---
name: "StateVarView"
section: "3"
platform: "linux"
package: "ivtools-dev"
version: "1.1.3-4"
release: "Debian 3.1 (Sarge)"
platforms: ["linux"]
url: "https://new.carta.tech/StateVarView"
---

# StateVarView(3)

state variable view base class

## NAME

StateVarView - state variable view base class

## SYNOPSIS

**#include \<Unidraw/stateview.h\>**

## DESCRIPTION

StateVarView is the base class for state variable views.  State variable views provide a graphical interface to examining and potentially modifying a state variable subject.  The StateVarView base class is an abstract class derived from MonoScene.  Like MonoScene, the StateVarView class is not instantiated; instead, subclasses add state and behavior appropriate for displaying and editing their subject.  Like other MonoScene subclasses, StateVarView subclasses use an interactor composition to define their appearance.

## PUBLIC OPERATIONS

- **virtual void Update()**

  Update the state variable view in response to a change in state it depends on (typically the subject's).  This operation does not normally need redefinition if Init and Stale (described below) are redefined.

## PROTECTED OPERATIONS

- **StateVarView(StateVar\*)**

  Subclass constructors normally take an instance of the corresponding subject as an argument.  The base class constructor automatically attaches the view to the subject.

- **virtual void Init()**

  Initialize the view based on information in the subject.  Subclasses redefine this operation according to their semantics; it does nothing by default.

- **virtual boolean Stale()**

  Return whether the view is in any way inconsistent with its subject. This operation always returns *true* by default; subclasses can redefine it to make a more discerning decision.

## SEE ALSO

MonoScene(3I), StateVar(3U)