Class: BufferedValueHolder

• Inheritance
• Description
• Class protocol
  • initialization
  • instance creation
• Instance protocol
  • accessing
  • accessing-channels
  • change & update
  • initialization
  • queries
• Examples

Inheritance:

   Object
   |
   +--Model
      |
      +--ValueModel
         |
         +--ValueHolder
            |
            +--BufferedValueHolder

Package:

stx:libview2

Category:

Interface-Support-Models

Version:

rev: 1.18 date: 2023/07/15 18:34:06

user: cg

file: BufferedValueHolder.st directory: libview2

module: stx stc-classLibrary: libview2

Description:

a bufferedValueHolder keeps a temporary copy of the realHolders value,
and only does a real store of the value when triggered.
Triggering is done by depending on a trigger object's value, which is
typically a ValueHolder on a boolean, which is set by an ok-button.

Notice: 
    this class was implemented using protocol information
    from alpha testers - it may not be complete or compatible to
    the corresponding ST-80 class. 
    If you encounter any incompatibilities, please forward a note 
    describing the incompatibility verbal (i.e. no code) to the ST/X team.

copyright
COPYRIGHT (c) 1995 by Claus Gittinger
             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:

 intialize

 subject: someModel triggerChannel: aTrigger

return a new BufferedValueHolder offering a buffered copy of someModels
value - only updating this value, when aTrigger changes to true.

Instance protocol:

 setValue: anObject

set my value without notification.

 subject: someModel

 value

return my value

 triggerChannel: aTrigger

 update: something with: aParameter from: changedObject

now, store the buffered value into the subject

 initialize

(comment from inherited method)
just to ignore initialize to objects which do not need it

 isBuffering

return true, if the receiver is currently buffering something
(i.e. its value has been assigned)

Examples:

    |firstName lastName dialog|

    firstName :=  'foo' asValue.
    lastName := 'bar' asValue.

    dialog := Dialog new.
    (dialog addTextLabel:'Name:') layout:#left.
    dialog addInputFieldOn:firstName.
    dialog addVerticalSpace.
    (dialog addTextLabel:'Address:') layout:#left.
    dialog addInputFieldOn:lastName.

    dialog addAbortButton; addOkButton.

    dialog open.

    Transcript show:firstName value; show:' '; showCR:lastName value

    |firstName lastName trigger dialog|

    firstName :=  'foo' asValue.
    lastName := 'bar' asValue.
    trigger := TriggerValue new.

    dialog := Dialog new.
    (dialog addTextLabel:'Name:') layout:#left.
    dialog addInputFieldOn:(BufferedValueHolder
                                subject:firstName
                                triggerChannel:trigger).
    dialog addVerticalSpace.
    (dialog addTextLabel:'Address:') layout:#left.
    dialog addInputFieldOn:(BufferedValueHolder
                                subject:lastName
                                triggerChannel:trigger).

    dialog addAbortButton; 
           addButton:(Button new 
                            label:'undo'; 
                            action:[trigger value:false]);
           addOkButton.

    dialog open.
    dialog accepted ifTrue:[
        trigger value:true
    ].

    Transcript show:firstName value; show:' '; showCR:lastName value