Class: ModelUpdateLockedQuery (private in Model

• Inheritance
• Description
• Class protocol
  • handling
  • queries
• Instance protocol
  • defaults

Inheritance:

   Object
   |
   +--GenericException
      |
      +--Notification
         |
         +--Query
            |
            +--Model::ModelUpdateLockedQuery

Package:

stx:libview2

Category:

Interface-Support-Models

Owner:

Model

Description:

this query can answer true (ie. ''isLocked'') for a particular model,
while inside a updating block.

This is used for temporal blocking models to be changed
(eg. to prevent cyclic updates).

A particular application of this is found in input-field + tree selection
combinations, where entering a new value into the field changes the treeselection,
and also tree selection changes the input field's value.
Concrete: take a look at the XMLInspector's xpath field, which triggers a tree
selection change, but the selection change should not backfire on the field in this
case, whereas a regular tree-selection will change the field.

Notice:
    do NOT place the query into the general value: method of Model.
    This is too expensive to be done every time.
    Thus, the related models need to know about the interlocking and
    must do this individually.

see example


[instance variables:]

[class variables:]

example
|vh1 vh2|

vh1 := ValueHolder new.
vh1 onChangeEvaluate:[
    (vh2 isLocked) ifFalse:[
        vh2 value: #newValue 
    ].
].

vh2 := ValueHolder new.
vh2 value:#oldValue.

vh2 withUpdatesLockedDo:[
    vh1 value:123.
].

because of the lock, the old value should still be there'.
self assert:(vh2 value == #oldValue)

Class protocol:

 answer: aBoolean for: aModel do: aBlock

evaluate aBlock, answering aBoolean if asked for the locking status of aModel

 isLocked: aModel

asking for the locking status of aModel

Instance protocol:

 defaultResumeValue