[Dev] Small tweak to parcel loader

[Morgen Sagen]

On Jun 11, 2004, at 1:05 PM, John Anderson wrote:

> Suppose I have two attributes:
>
>    <Attribute itemName="parentBlock">
>      <type itemref="docSchema:Block"/>
>      <cardinality>single</cardinality>
>      <inverseAttribute itemref="docSchema:Block/childrenBlocks"/>
>      <defaultValue itemref="None"/>
>    </Attribute>
>    <Attribute itemName="childrenBlocks">
>      <type itemref="docSchema:Block"/>
>      <cardinality>list</cardinality>
>      <inverseAttribute itemref="docSchema:Block/parentBlock"/>
>      <initialValue/>
>    </Attribute>
>
> I would assume that block.parent block would never throw an  
> AttributeNotFound exception. However, in my code it does. Is this a  
> bug or is the data model too complicated for me to understand?
>
> John

Hmm, I just added a minimal parcel in the unit tests which has two  
attributes similar to what you have, and when I test it, parentBlock is  
being set to None.  You can see the XML here:

http://cvs.osafoundation.org/viewcvs.cgi/chandler/repository/parcel/ 
tests/testparcels/collections/parcel.xml?rev=HEAD&content-type=text/ 
vnd.viewcvs-markup

However, if I create three items, parent, child1 and child2, and do:

child1.parentBlock = parent
child2.parentBlock = parent
for child in parent.childrenBlocks:
    print child, child.parentBlock

...I get an exception:

Traceback (most recent call last):
   File "TestCollections.py", line 35, in testCollections
     for child in parent.childrenBlocks:
   File "/Users/morgen/dev/chandler/repository/util/LinkedMap.py", line  
238, in __iter__
     yield self[key]
   File "/Users/morgen/dev/chandler/repository/item/ItemRef.py", line  
528, in __getitem__
     return self._getRef(key).other(self._getItem())
   File "/Users/morgen/dev/chandler/repository/item/ItemRef.py", line  
126, in other
     raise ValueError, "%s doesn't reference %s" %(self, item)
ValueError: <ItemRef: <Item: child1  
49783b2a-bc10-11d8-a380-000a95bb2738> - <Item: parent  
4976fb48-bc10-11d8-a380-000a95bb2738>> doesn't reference <Kind: Block  
4970bd8c-bc10-11d8-a380-000a95bb2738>

I suspect that this has something to do with the way the parcel loader  
is calling the repo API to set the initialValue of the childrenBlocks  
attribute to an empty list:

     attributeItem.addValue("initialValue", [ ] )

Perhaps Andi can set me straight as to the proper way to use the API to  
specify an initialValue of empty list (or dict).

~morgen


> Morgen Sagen wrote:
>
>> By popular demand:  if you want to set the defaultValue or  
>> initialValue of a list or dict attribute to be an empty list or dict,  
>> you may now include either "<defaultValue/>" or "<initialValue/>"  
>> inside that attribute's definition.  For example:
>>
>>   <Attribute itemName="listAttr">
>>     <displayName>List Attribute</displayName>
>>     <cardinality>list</cardinality>
>>     <type itemref="String"/>
>>     <initialValue/>
>>   </Attribute>
>>
>> ~morgen
>>
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