Class: IndirectValue

• Inheritance
• Description
• Class protocol
  • instance creation
• Instance protocol
  • accessing
  • change & update
• Examples

Inheritance:

   Object
   |
   +--Model
      |
      +--ValueModel
         |
         +--IndirectValue

Package:

stx:libview2

Category:

Interface-Support-Models

Version:

rev: 1.12 date: 2023/07/15 18:33:29

user: cg

file: IndirectValue.st directory: libview2

module: stx stc-classLibrary: libview2

Description:

IndirectValue refers to another valueHolder and presents that holder's value
as my own value.
However, the holder can be changed, which results in a change message from myself.

Can be used if a valueHolder is needed which represents different values over
time, for example, a line/column holder for a notebook-like multi-codeView 
application, where the line/col holder is switched whenever the tab is switched.
(use an IndirectValue as holder of the line/col labels).

Another possible use is to synchronize two notebools via a common valueHolder,
which is used as indirect-value for the two individual indirect-selection-valueholders.

copyright
COPYRIGHT (c) 2003 by eXept Software AG
             All Rights Reserved

This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice.   This software may not
be provided or otherwise made available to, or used by, any
other person.  No title to or ownership of the software is
hereby transferred.

Class protocol:

 for: aValueHolder

return a new IndirectValue presenting aValueHolder

Instance protocol:

 setValue: newValue

physically set my value, without change notifications

 setValueHolder: aValueHolder

change my holder

 value

return my value

 valueHolder

return my valueHolder

 valueHolder: aValueHolder

change my holder

 update: something with: aParameter from: someone

the holder I depend on has changed - send a change notification to my dependents

Examples:

    |holder1 holder2 indirVal lbl|

    holder1 := '1' asValue.
    holder2 := '2' asValue.
    indirVal := IndirectValue for:holder1.

    lbl := Label new.
    lbl labelChannel:indirVal.
    lbl open.
    lbl waitUntilVisible.
    
    Delay waitForSeconds:2.
    indirVal valueHolder:holder2.

    Delay waitForSeconds:2.
    indirVal valueHolder:holder1.