Class: ProtocolAdaptor

• Inheritance
• Description
• Related information
• Class protocol
  • instance creation
• Instance protocol
  • accessing
  • accessing-spec
  • change & update
  • initialization
• Examples

Inheritance:

   Object
   |
   +--Model
      |
      +--ValueModel
         |
         +--ProtocolAdaptor
            |
            +--AspectAdaptor
            |
            +--DictionaryAdaptor

Package:

stx:libview2

Category:

Interface-Support-Models

Version:

rev: 1.15 date: 2014/03/05 22:13:03

user: cg

file: ProtocolAdaptor.st directory: libview2

module: stx stc-classLibrary: libview2

Author:

Claus Gittinger

Description:

a ProtocolAdaptor allows access to embeded values in a
complex model and plays model towards the outside world.

Consider the case where editFields are required for the
elements (instance variables) of a more complex model.
Using ValueHolders, you had to copy the individual
values out-of and into multiple valueHolders.
A protocolAdaptor makes this easier, by playing model towards
the editField, returning a value from the complex model, 
and forwards changes to the complex model.

Notice: 
    since you can specify the aspect- and changeSymbols in most ST/X
    widgets, ProtocolAdapters are not always needed 
    (at least, if no accesspath is required). 
    However, if you want to apply widgets on objects which where not 
    originally designed as models (such as Arrays), ProtocolAdapters 
    are very handy.

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.

Related information:

    Model
    AspectAdaptor
    ValueHolder

Class protocol:

 accessPath: aCollectionOfSelectors

 subject: anObject

 subject: anObject accessPath: aCollectionOfSelectors

 subject: anObject sendsUpdates: aBoolean

 subject: anObject sendsUpdates: aBoolean accessPath: aCollectionOfSelectors

 subjectChannel: aValueHolder

 subjectChannel: aValueHolder accessPath: aCollectionOfSelectors

 subjectChannel: aValueHolder sendsUpdates: aBoolean

 subjectChannel: aValueHolder sendsUpdates: aBoolean accessPath: aCollectionOfSelectors

Instance protocol:

 setValue: newValue

set the value in my subject or subjectChannel.

 setValue: newValue usingSubject: anObject

set a value in anObject, using the selectors in accessPath.
A helper for setValue:.

 subjectValue

return the value from my subject or subjectChannel.

 value

return the value from my subject or subjectChannel.

 value: newValue

set my value & send change notifications to my dependents
if it changed. But only if my subject does not itself
send change notifications (otherwise, we'd send double notifications).

 valueUsingSubject: anObject

return the value from anObject, using the selectors in accessPath.
A helper for value.

 accessPath

return the access path

 accessPath: aCollectionOfSelectors

set the access path

 subject

return the subject

 subject: anObject

set the subject

 subjectChannel

return the subjectChannel

 subjectChannel: aValueHolder

set the subjectChannel

 subjectSendsUpdates

return true, if the subject sends updates itself
If true, the receiver will not send updates on changes

 subjectSendsUpdates: aBoolean

set/clear the flag which states if the subject sends updates itself.
If true, the receiver will not send updates on changes

 update: something with: aPArameter from: changedObject

translate updates from my subject into value-changes towards
my dependents. Since I have no specific aspect, every change is forwarded

 initialize

setup, assuming that the subject does not send change notifications

Examples:

        |a obj|

        a := ProtocolAdaptor accessPath:#(1 2 3).
        obj := Array with:#(11 (121 122 123) 13)
                     with:#(21 (221 222 223) 23)
                     with:#(33 (321 322 323) 33).
        a valueUsingSubject:obj  

        |a obj|

        a := ProtocolAdaptor accessPath:#(1 2 origin).
        obj := Array with:(Array with:1@1 with:(1@2 corner:100@100))
                     with:(Array with:2@1 with:2@2)
                     with:(Array with:3@1 with:3@2).
        a valueUsingSubject:obj  

        |a model|

        a := ProtocolAdaptor accessPath:#(1 2 origin).
        model := (Array with:(Array with:1@1 with:(1@2 corner:100@100))
                     with:(Array with:2@1 with:2@2)
                     with:(Array with:3@1 with:3@2)) asValue.
        a subjectChannel:model.
        a value