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Class: BlockValue


Inheritance:

   Object
   |
   +--Model
      |
      +--ValueModel
         |
         +--BlockValue
            |
            +--BooleanBlockValue

Package:
stx:libview2
Category:
Interface-Support-Models
Version:
rev: 1.31 date: 2017/03/31 14:31:43
user: stefan
file: BlockValue.st directory: libview2
module: stx stc-classLibrary: libview2
Author:
Claus Gittinger

Description:


BlockValues depend on multiple other objects (typically valueHolders)
and recompute a value whenever one of them changes.
If the new value is different, it triggers itself a change to its dependents.

Example use is to base an enableChannels value on multiple other boolean values.
(See example for how this is done)

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.

Warning:
    BlockValues only work ine one direction; changing the blockValue's value
    does not affect the original model's value.


Class protocol:

initialization
o  initialize

instance creation
o  block: aBlock arguments: aCollectionOfArguments
return a new BlockValue computing aBlock.
Same as #with:arguments: for ST80 compatibility

o  forLogical: arg1 and: arg2
return a new BlockValue computing the logical AND of its args
(which are usually other valueHolders)

o  forLogical: arg1 and: arg2 and: arg3
return a new BlockValue computing the logical AND of its args
(which are usually other valueHolders)

o  forLogical: arg1 or: arg2
return a new BlockValue computing the logical OR of its args
(which are usually other valueHolders)

o  forLogical: arg1 or: arg2 or: arg3
return a new BlockValue computing the logical OR of its args
(which are usually other valueHolders)

o  forLogicalAndAll: argArray
return a new BlockValue computing the logical AND of all elements
in the passed argArray (which are usually other valueHolders)

o  forLogicalNot: arg
return a new BlockValue computing the logical NOT of its arg
(which is usually another valueHolder)

o  forLogicalOrAll: argArray
return a new BlockValue computing the logical OR of all elements
in the passed argArray (which are usually other valueHolders)

o  forValue: someValue equalTo: someConstant
return a new BlockValue generating a true,
if someValue (usually another holder) contains a value equal to someConstant.
Useful, if the other valueHolder is a radioButton group model,
and you want to automatically enable/disable other items based on the value
(i.e. via the enableChannel)

o  with: aBlock
return a new BlockValue computing aBlock

o  with: aBlock argument: anArgument
return a new BlockValue computing aBlock

o  with: aBlock argument: anArgument1 argument: anArgument2
return a new BlockValue computing aBlock

o  with: aBlock argument: anArgument1 argument: anArgument2 argument: anArgument3
return a new BlockValue computing aBlock

o  with: aBlock argument: anArgument1 argument: anArgument2 argument: anArgument3 argument: anArgument4
return a new BlockValue computing aBlock

o  with: aBlock arguments: aCollectionOfArguments
return a new BlockValue computing aBlock


Instance protocol:

accessing
o  setArguments: aCollectionOfArguments
set the receiver's arguments to be passed to it.
A change in any of the arguments will force reevaluation of the action
block - possibly generating another change from myself

o  setBlock: aBlock
set the receiver's action block

o  setBlock: aBlock argumentArray: anArgumentCollection
set the receiver's action block, and define an arguments collection
to be passed to it.
A change in any element of the collection will force reevaluation of the
action block (passing the collection as a single argument)
- possibly generating another change from myself

o  setBlock: aBlock arguments: aCollectionOfArguments
set the receiver's action block, and define arguments to be passed to it.
A change in any of the arguments will force reevaluation of the action
block - possibly generating another change from myself

o  setValue: newValue
physically set my value, without change notifications.
This is a noop here, since my value is computed.

o  value
retrieve my value - this does not always evaluate the action block,
since the returned value is cached internally

change & update
o  recomputeValue
reevaluate my actionBlock, and possibly send a change notification to my dependents

o  update: something with: aParameter from: someone
the one I depend on has changed - reevaluate my actionBlock,
and possibly send a change notification to my dependents

dependents access
o  release
release any dependencies upon the arguments

misc
o  computeValue
evaluate the receiver's action block

o  dependOn: someObject
arrange for the blockValue to be reevaluated, whenever someObject
changes (i.e. sends a change notification)

o  resetValue
evaluate the receiver's action block


Examples:


checkToggle 3 shows the value of toggle1 AND toggle2
    |val1 val2 both box|

    val1 := false asValue.
    val2 := false asValue.
    both := BlockValue 
                with:[:v1 :v2 | 
                        Transcript showCR:'evaluating ...'.
                        v1 value and:[v2 value]
                     ] 
                arguments:(Array with:val1 with:val2).

    box := Dialog new.
    box addCheckBox:'one' on:val1.
    box addCheckBox:'two' on:val2.
    box addHorizontalLine.
    box addCheckBox:'both' on:both.
    box addOkButton.
    box open
the same, using a convenient instance creation message:
    |val1 val2 both box|

    val1 := false asValue.
    val2 := false asValue.
    both := BlockValue forLogical:val1 and:val2.

    box := Dialog new.
    box addCheckBox:'one' on:val1.
    box addCheckBox:'two' on:val2.
    box addHorizontalLine.
    (box addCheckBox:'both' on:both) disable.
    box addOkButton.
    box open
logical or:
    |val1 val2 both box|

    val1 := false asValue.
    val2 := false asValue.
    both := BlockValue forLogical:val1 or:val2.

    box := Dialog new.
    box addCheckBox:'one' on:val1.
    box addCheckBox:'two' on:val2.
    box addHorizontalLine.
    box addCheckBox:'both' on:both.
    box addOkButton.
    box open
example use: enabling an element depending on two others:
    |val1 val2 enabler val3 box|

    val1 := false asValue.
    val2 := false asValue.
    val3 := false asValue.
    enabler := BlockValue forLogical:val1 and:val2.

    box := Dialog new.
    box addCheckBox:'one' on:val1.
    box addCheckBox:'two' on:val2.
    box addHorizontalLine.
    (box addCheckBox:'three (both of the above)' on:val3) enableChannel:enabler.
    box addOkButton.
    box open
like above, using a logical-or block:
    |val1 val2 enabler val3 box|

    val1 := false asValue.
    val2 := false asValue.
    val3 := false asValue.
    enabler := BlockValue forLogical:val1 or:val2.

    box := Dialog new.
    box addCheckBox:'one' on:val1.
    box addCheckBox:'two' on:val2.
    box addHorizontalLine.
    (box addCheckBox:'three (any of the above)' on:val3) enableChannel:enabler.
    box addOkButton.
    box open
like above, using a bunch of toggles:
    |values anyValue box|

    values := (1 to:10) collect:[:i | false asValue].
    anyValue := BlockValue forLogicalOrAll:values.
    anyValue onChangeSend:#value to:[Transcript showCR:'any is true'].

    box := Dialog new.
    values keysAndValuesDo:[:index :aValueHolder |
        box addCheckBox:index printString on:aValueHolder.
    ].
    box addHorizontalLine.
    (box addOkButton) enableChannel:anyValue.
    box open


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