I was interested in creating a generic helper function to get the
instrumented list associated with a "RelationshipProperty" for a Model,
you can get the relationship from
inspect(model).mapper.relationships.items(), but the relationship is just
the RelationshipProperty object and *not* the InstrumentedList. I could
not see a way to get the instrumented list from the relationship and was
wondering if I was missing something or if we really must use
getattr(model, property_name) to get the InstrumentedList.
I also noticed that I couldn't directly set the instrumented list values
from the relationship; I can do add/remove/extend operations on the list
but not e.g. `relationship = [item1, item2, item3,]`, for that I had to use
setattr(model, relationship_name, values_array)
Any feedback on my approach or if there is a better way to do this would be
appreciated!
def type_query(type, id):
type_query = g.session.query(type).filter_by(id=id).one()
return type_query
def get_relationship_from_model(parent_entity, relationship_model):
relationship_label = None
for label, r in inspect(parent_entity).mapper.relationships.items():
if r.entity.class_ == relationship_model:
relationship_label = label
break
relationship = getattr(parent_entity, relationship_label)
return relationship_label, relationship
def update_list(relationship_model, entity_model, operation: str, id_list:
Optional[List[UUID]] = None):
"""
id list = ids to add or remove from relationship
relationship_type = the `type` of the relationship on entity model, e.g...
entity_model = the model whose relationships are being updated
operation = add or remove
:param id_list:
:param relationship_model:
:param entity_model:
:param operation:
:return:
"""
if not id_list:
return entity_model
# e.g. CvMeasurementAttribute -> cv_measurement_attributes
relationship_label, relationship =
get_relationship_from_model(parent_entity=entity_model,
relationship_model=relationship_model)
entities_to_relate = [
type_query(type=relationship_model, id=id_) for id_ in id_list
]
if operation == "add":
relationship.extend(entities_to_relate)
elif operation == "remove":
for entity in entities_to_relate:
relationship.remove(entity)
else:
setattr(entity_model, relationship_label, entities_to_relate)
return entity_model
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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