Final version:
def walk_related(obj, enableDuplicates=False, level=-1, memo=None):
memo = memo or set()
insp = inspect(obj)
for relobj in insp.mapper.cascade_iterator('delete', insp):
if enableDuplicates or relobj[0] not in memo:
memo.add(relobj[0])
yield level, relobj[0]
relatedObjects = walk_related(relobj[0],
enableDuplicates=enableDuplicates, level=level + 1, memo=
memo)
for walked_relobj in relatedObjects:
yield walked_relobj
Dne pondělí 14. září 2015 11:57:05 UTC+2 Pavel S napsal(a):
>
> Hi,
>
> I just realized that I need your first solution, since I need to get only
> those objects that would cascade in case of deletion.
>
> But thanks anyhow...
>
> P
>
> Dne čtvrtek 10. září 2015 15:35:39 UTC+2 Michael Bayer napsal(a):
>>
>>
>>
>> On 9/10/15 8:48 AM, Pavel S wrote:
>>
>> Let's say, I have declarative classes A, B, C, D.
>>
>> A is the parent
>> B has FK&relationship to A
>> C has FK&relationship to B,
>> D has FK&relationship to C etc...
>>
>> I'd like to implement *generic method* walk(obj) which will recursively
>> yield dependent/related objects of obj (which is instance of A).
>>
>> I know that there is introspection interface inspect(), however I'm
>> don't really understand how to use it properly in my use case.
>>
>> Shall I do inspect(obj) or rather inspect(obj.__class__) and then
>> somehow apply inspection to obj?
>>
>> Are there an examples and best practices?
>>
>> right now you can kind of get this effect using cascade_iterator:
>> http://docs.sqlalchemy.org/en/rel_1_0/orm/mapping_api.html?highlight=cascade_iterator#sqlalchemy.orm.mapper.Mapper.cascade_iterator
>>
>> the limitation is that right now its based on relationship cascade
>> settings, as that's what it was intended for, so you'd probably want to use
>> "save-update":
>>
>> insp = inspect(my_object)
>> for obj in insp.mapper.cascade_iterator("save-update", insp):
>> # ...
>>
>> to implement your own system, the graph of objects is strictly based on
>> relationship. so walk() is pretty simple:
>>
>> def walk(obj):
>> yield obj
>> insp = inspect(obj)
>> for relationship in insp.mapper.relationships:
>> related = getattr(obj, relationship.key)
>> if relationship.uselist:
>> for collection_member in related:
>> for walk_related in walk(collection_member):
>> yield walk_related
>> elif related is not None:
>> for walk_related in walk(related):
>> yield walk_related
>>
>>
>>
>>
>>
>>
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