[Zope] Multiple inheritance and tree data structure problems

[peter sabaini]

take a look at

http://debian.acm.ndsu.nodak.edu/doc/python-extclass/ExtensionClass.html

search for 'inheritedAttribute'


Manuel_Montejo@apb.es wrote:
 > Hi,
 >
 > I'm developing a Zope product, ServiceProduct,  that behaves as a 
Node in a
 > Tree data structure.
 >
 > The class hierachy is the following    [<--- : extends ; <- - - :
 > implements]
 >
 > Base <---Tree <- - -TreeImpl
 > Base <---- TreeNode <- - -  TreeNodeImpl
 > Base <---- Service
 >
 > Implicit,Persistent,RoleManager,ObjectManager,PropertyManager,Item <----
 > ProductBase
 > ProductBase, TreeNodeImpl<---- ServiceProduct
 > TreeNode<- - - ServiceProduct
 > Service<- - - ServiceProduct
 >
 > So, when I create an new instance of ServiceProduct using the ZMI I 
found a
 > problem with the constructor. The
 > error message is
 >      "unbound method __init__() must be called with instance as first
 > argument"
 > and the code is
 >
 >     def __init__(self, id):
 >         ProductBase.__init__(self,id,'')
 >         try:
 >             TreeNodeImpl.__init__(self,id)
 >         except Exception, e:
 >             print 'Problems with TreeNodeImpl constructor', e
 >             # do TreeNodeImpl initialization here if fails
 >             self.setNombre( id )
 >             self.parentNode = None
 >             self.children = []
 >             self.tree = None
 >
 > I hope that doing the TreeNodeImpl initialization in the except 
clause will
 > solve this problem.
 >
 > Then, I add child ServiceProduct objects to the tree hierarchy but it 
seems
 > that the references between parent
 > and child objects change when new calls to the object are done (I use a
 > DTML page for displaying hierarchy info).
 >
 > Even worse, the ProductBase has a method hashCode that shows instance 
info
 >
 >     def hashCode(self):
 >         id = str( self )
 >         id = id.replace( '<', '_')
 >         id = id.replace( '>', '_')
 >         id = id.replace( ' ', '_')
 >         return id
 >
 > returns two different results when is called from a DTML page, (sometimes
 > the first and other times the second),
 > BUT I have created only one instance of the object.
 >
 > Finally, I have tested the TreeImpl, TreeNodeImpl outside Zope and it 
works
 > without any problems.
 >
 > Any idea of where is the problem? The 'constructor problem' is related to
 > the 'references losing' problem?
 > Any help with will be apreciated.
 >
 > Best regards,
 >
 > Manu
 >
 >
 >
 >
 >
 >
 >
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