def compute_objs_diff(self, data, objs, instance):
"""
Find out the right number of related objects to be saved,
given the data and the objects that are already present.
:param data: list of data for sub forms
:param objs: objs that are already there
:param instance: a model instance
"""
objs_to_delete = []
diff = len(data) - len(objs)
# manage obj addition
if diff > 0:
kwargs = {self.origin_model_name: instance}
objs = chain(
objs,
repeat_lambda(lambda: self.foreign_model(**kwargs), diff)
)
# manage obj deletion
elif diff < 0:
objs, objs_to_delete = isplit(objs, len(data))
return objs, objs_to_delete
def test_isplit(self):
_in = [1, 2, 3]
q, r = python.isplit(_in, 2)
q, r = list(q), list(r)
self.assertEqual(q, [1, 2])
self.assertEqual(r, [3])