Re: [sqlalchemy] Multi-values custom mapped collection

[Antonio Beamud Montero]

El 01/06/12 16:59, Michael Bayer escribió:

@appender needs to be a method that just accepts a mapped object to be added to 
the collection.   then, @internally_instrumented is needed to prevent the 
collections system from placing additional insturmentation on standard methods 
like __setitem__.   Also building custom dictionary collections is very 
difficult in any case (for me as well) so you were close, and that's pretty 
good !

A lot of thanks, Michael.. now it it works like a charm ;-)

class MyMappedCollection(dict):
     def __init__(self, data=None):
         if data:
             self.update(data)

     @collection.appender
     def _add_perm(self, pobj):
         l = dict.setdefault(self, pobj.permission, [])
         l.append(pobj)

     @collection.internally_instrumented
     def __setitem__(self, permission, pobj):
         self._add_perm(pobj)

     @collection.remover
     def _remove(self, perm):
         self[perm.permission].remove(perm)

     @collection.iterator
     def __iter__(self):
         for vals in self.itervalues():
             for perm in vals:
                 yield perm



On Jun 1, 2012, at 9:38 AM, Antonio Beamud Montero wrote:

Hi all:
I'm trying to implement a permission system usign polymorphic associations. In 
my example only one object has permissions associated (ULine).
The problem is trying to use a mapping with permission names as keys, and 
values Permission objects with a 1:1 user relation.
A complete example here:

http://pastebin.com/SqCfBCFp

But I can't get this working, the next error is raised:

    child_state, child_dict = instance_state(child), \
AttributeError: 'list' object has no attribute '_sa_instance_state'

A lot of thanks.

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