'From Smalltalk/X, Version:2.10.5 on 9-may-1995 at 12:03:43 pm'!

ValueModel subclass:#ProtocolAdaptor

	 instanceVariableNames:'accessPath subject subjectChannel subjectSendsUpdates'

	 classVariableNames:''

	 poolDictionaries:''

!

!ProtocolAdaptor class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1995 by Claus Gittinger

 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.

"

!

version

"

"

!

documentation

"

    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 access-

    path is required). 

    However, if you want to apply widgets on objects which where not originally 

    designed as models (such as Arrays), ProtocolAdapters are very useful.

    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 to the ST/X team.

"

!

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   

"

! !

!ProtocolAdaptor class methodsFor:'instance creation'!

accessPath:aCollectionOfSelectors

    ^ (self new) accessPath:aCollectionOfSelectors

!

subject:anObject

    ^ (self new) subject:anObject

!

subject:anObject sendsUpdates:aBoolean

    ^ (self new) subject:anObject; sendsUpdates:aBoolean

!

subject:anObject accessPath:aCollectionOfSelectors

    ^ (self new) subject:anObject; accessPath:aCollectionOfSelectors

!

subject:anObject sendsUpdates:aBoolean accessPath:aCollectionOfSelectors

    ^ (self new) subject:anObject; sendsUpdates:aBoolean; accessPath:aCollectionOfSelectors

!

subjectChannel:aValueHolder

    ^ (self new) subjectChannel:aValueHolder

!

subjectChannel:aValueHolder sendsUpdates:aBoolean 

    ^ (self new) subjectChannel:aValueHolder; sendsUpdates:aBoolean

!

subjectChannel:aValueHolder accessPath:aCollectionOfSelectors

    ^ (self new) subjectChannel:aValueHolder; accessPath:aCollectionOfSelectors

!

subjectChannel:aValueHolder sendsUpdates:aBoolean accessPath:aCollectionOfSelectors

    ^ (self new) subjectChannel:aValueHolder; sendsUpdates:aBoolean; accessPath:aCollectionOfSelectors

! !

!ProtocolAdaptor methodsFor:'accessing'!

setValue:newValue usingSubject:anObject

    "set a value in anObject, using the selectors in accessPath.

     A helper for setValue:."

    |obj lastIndex|

    obj := anObject.

    lastIndex := accessPath size.

    accessPath keysAndValuesDo:[:idx :aSelectorOrIndex |

	aSelectorOrIndex isInteger ifTrue:[

	    idx == lastIndex ifTrue:[

		obj at:aSelectorOrIndex put:newValue

	    ] ifFalse:[

		obj := obj at:aSelectorOrIndex

	    ]

	] ifFalse:[

	    idx == lastIndex ifTrue:[

		obj perform:(aSelectorOrIndex , ':') asSymbol with:newValue

	    ] ifFalse:[

		obj := obj perform:aSelectorOrIndex

	    ]

	]

    ].

    ^ newValue

!

valueUsingSubject:anObject

    "return the value from anObject, using the selectors in accessPath.

     A helper for value."

    |obj|

    obj := anObject.

    accessPath notNil ifTrue:[

	accessPath do:[:aSelectorOrIndex |

	    aSelectorOrIndex isInteger ifTrue:[

		obj := obj at:aSelectorOrIndex

	    ] ifFalse:[

		obj := obj perform:aSelectorOrIndex

	    ]

	].

    ].

    ^ obj

!

value

    "return the value from my subject or subjectChannel."

    |obj|

    subject notNil ifTrue:[

	obj := subject.

    ] ifFalse:[

	obj := subjectChannel value

    ].

    ^ self valueUsingSubject:obj

!

setValue:newValue

    "set the value in my subject or subjectChannel."

    |obj|

    subject notNil ifTrue:[

	obj := subject.

    ] ifFalse:[

	obj := subjectChannel value

    ].

    ^ self setValue:newValue usingSubject:obj

! !

!ProtocolAdaptor methodsFor:'change notification'!

notifyChange

    subjectSendsUpdates ifFalse:[

    ]

! !

!ProtocolAdaptor methodsFor:'initialization'!

initialize

    super initialize.

    subjectSendsUpdates := false. 

! !

!ProtocolAdaptor methodsFor:'change & update'!

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"

    (changedObject == subject

    or:[changedObject == subjectChannel]) ifTrue:[

	self changed:#value.

	^ self

    ].

! !

!ProtocolAdaptor methodsFor:'accessing-spec'!

subjectSendsUpdates

    "return true, if the subject sends updates itself

     If true, the receiver will not send updates on changes"

    ^ subjectSendsUpdates

!

subjectSendsUpdates:aBoolean

    "set/clear the flag which states if the subject sends updates itself.

     If true, the receiver will not send updates on changes"

    subjectSendsUpdates := aBoolean.

!

subjectChannel:aValueHolder

    |oldChannel|

    oldChannel := subjectChannel.

    subjectChannel := aValueHolder.

    oldChannel notNil ifTrue:[

	self changed:#value.

    ].

!

subjectChannel

    ^ subjectChannel

!

subject:anObject

    subject notNil ifTrue:[

	subject removeDependent:self

    ].

    subject := anObject.

    self changed:#value.

    subject notNil ifTrue:[

	subject addDependent:self

    ].

!

subject

    ^ subject

!

accessPath:aCollectionOfSelectors

    accessPath := aCollectionOfSelectors

!

accessPath

    ^ accessPath

! !