Class: SelectionInList

• Inheritance
• Description
• Related information
• Class protocol
  • instance creation
• Instance protocol
  • accessing-holders
  • accessing-values
  • change & update
  • initialization
  • obsolete-backward compatibility
  • printing & storing
  • private
  • queries
• Examples

Inheritance:

   Object
   |
   +--Model
      |
      +--ValueModel
         |
         +--ValueHolder
            |
            +--SelectionInList
               |
               +--MultiSelectionInList

Package:

stx:libwidg

Category:

Interface-Support-Models

Version:

rev: 1.35 date: 2019/06/28 07:12:15

user: cg

file: SelectionInList.st directory: libwidg

module: stx stc-classLibrary: libwidg

Author:

Claus Gittinger

Description:

Instances of SelectionInList can be used as model for
a SelectionInListView or a PopUpList. 
They keep two values: a list value and a selection value; 
both are referred to via valueHolders.

If any of those two changes, the selectionInList notifies its 
dependents via a change notification, 
using #list or #selectionIndex as update aspect respectively.

A popupList also knows how to deal with a selectionInList model;
this makes it possible to have popupLists be somewhat exchangable
with selectionInListViews.

SelectionInLists only support a single selection within the list;
use MultiSelectionInList, if multiple selections are needed.

[instance variables:]
    listHolder              <ValueHolder>           holds the list
    selectionIndexHolder    <ValueHolder>           holdes the selectionIndex

Related information:

    SelectionInListView
    PopUpList
    MultiSelectionInList
    Model
    ValueHolder

Class protocol:

 with: aList

return a new instance holding aList

 with: aList initialSelection: index

return a new instance holding aList and initially selecting
the item at index.

Instance protocol:

 listHolder

return the valueHolder which holds the list

 listHolder: aValueHolder

set the valueHolder which holds the list.
Q: should we forward a change-notification ?

 selectionHolder

return someone holding on the selection itself (not the index).
Since we have no one, create an adapter, to get up-to-date values.

 selectionIndexHolder

return the valueHolder which holds the index

 selectionIndexHolder: aValueHolder

set the valueHolder which holdes the index.
Q: should we forward a change-notification ?

 list

return the list - that's the thingy held by the listHolder

 list: aCollection

set the list - that's the thingy held by the listHolder

 selection

return the selections value (i.e. the entry in the list - not its index).
If nothing is selected, nil is returned.

 selection: anObject

set the selection to be anObject.
If anObject is not in the list, the selection is cleared

 selectionIndex

return the selections index (1..).
That's the thingy held by the indexHolder.
For ST-80 compatibility, 0 is returned if nothing is selected.

 selectionIndex: newIndex

set the selectionIndex

 update: something with: aParameter from: changedObject

whenever one of my holders value changes,
tell my dependents about this

 initialize

initialize; create the valueHolders for the index and the list

 index

return the selections index.
This is an OBSOLETE backward compatibility interface

** This is an obsolete interface - do not use it (it may vanish in future versions) **

 index: newIndex

set the selections index.
This is an OBSOLETE backward compatibility interface

** This is an obsolete interface - do not use it (it may vanish in future versions) **

 indexHolder

return the valueHolder of the selections index.
This is an OBSOLETE backward compatibility interface

** This is an obsolete interface - do not use it (it may vanish in future versions) **

 indexHolder: aValueHolder

set the valueHolder of the selections index.
This is an OBSOLETE backward compatibility interface

** This is an obsolete interface - do not use it (it may vanish in future versions) **

 displayOn: aGCOrStream

Compatibility
append a printed desription on some stream (Dolphin, Squeak)
OR:
display the receiver in a graphicsContext at 0@0 (ST80).
This method allows for any object to be displayed in some view
(although the fallBack is to display its printString ...)

 clearSelection

clear the selection.
For ST-80 compatibility, a non-selection has an index of 0
although, nil sounds more natural to me ... (sigh)

 hasSelection

return true, if there is a selection

 numberOfSelections

return the number of selected entries

 zeroIndex

return the selections index returned when nothing
is selected. This method is provided to allow applications
to deal transparently with SelectionInList models AND with
MultSelectionInList models, which use different no-selection values.
Although I would prefer nil, ST-80 uses 0 to represent `no-selection'. (sigh)

Examples:

  |m v|

  m := SelectionInList new.
  m list:#('one' 'two' 'three' 'four').
  m selectionIndex:2.

  v := SelectionInListView on:m.
  v open

  |m v|

  m := SelectionInList new.
  m list:#('one' 'two' 'three' 'four').
  m selectionIndex:2.

  v := PopUpList on:m.
  v open

  |m v|

  m := SelectionInList 
              with:#('one' 'two' 'three' 'four')
              initialSelection:2.

  v := PopUpList on:m.
  v open

  |m v1 v2|

  m := SelectionInList new.
  m list:#('one' 'two' 'three' 'four').
  m selectionIndex:2.

  v1 := PopUpList on:m.
  v1 open.

  v2 := SelectionInListView on:m.
  v2 open

  |m v1 v2 b numItems|

  numItems := 4.

  m := SelectionInList new.
  m list:((1 to:numItems) collect:[:i | i printString]).
  m selectionIndex:2.

  v1 := ScrollableView forView:(SelectionInListView on:m).
  v1 open.

  v2 := ScrollableView forView:(SelectionInListView on:m).
  v2 open.

  b := Button label:'add item'.
  b action:[numItems := numItems + 1.
            m list:((1 to:numItems) collect:[:i | i printString]).
           ].
  b open