I have a function with a number of parameters, then a specialized instantiation of that function, with some settings for each of the function's parameters. So I have a structure like the following:
class Function(models.Model):
name = models.CharField()
class FunctionParameter(models.Model):
function = models.ForeignKey(Function)
class FunctionInstantiation(models.Model):
function = models.ForeignKey(Function)
class ParameterSetting(models.Model):
function_instantiation = models.ForeignKey(FunctionInstantiation)
function_parameter = models.ForeignKey(FunctionParameter)
In FunctionFactory I can use factory.RelatedFactory to create the parameters.
But in FunctionInstantiationFactory I can't use factory.RelatedFactory(ParameterSetting) to create ParameterSettings, because I don't have access to the parameter objects created within FunctionFactory, so I can't set parameter_setting.function_parameter_id.
How can FunctionInstantiationFactory look up the parameter_id of parameters created in FunctionFactory? Can I get at them from the return value of RelatedFactory(FunctionFactory)? Or do I need to look at the database?
This is Xelnor's answer, but fixes the bug so that only one function_instantiation is created, rather than one for each parameter/parameter_setting pair.
class FunctionFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.Function
name = factory.Sequence(lambda n: "Function %d" % n)
class FunctionParameterFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.FunctionParameter
function = factory.SubFactory(FunctionFactory)
class FunctionInstantiationFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.FunctionInstantiation
function = factory.SubFactory(FunctionFactory)
class ParameterSettingFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.ParameterSetting
function_instantiation = factory.SubFactory(FunctionInstantiationFactory)
function_parameter = factory.SubFactory(FunctionParameterFactory,
function=factory.SelfAttribute('..function_instantiation.function'))
class FunctionToParameterSettingsFactory(FunctionInstantiationFactory):
class Meta:
model = models.FunctionInstantiation
# This overrides the function_instantiation created inside
# ParameterSettingFactory, which then overrides the Function creation,
# with the SelfAttribute('..function_instantiation.function') syntax.
parameter_setting_1 = factory.RelatedFactory(ParameterSettingFactory,
'function_instantiation')
parameter_setting_2 = factory.RelatedFactory(ParameterSettingFactory,
'function_instantiation')
The following demonstrates the solutions to a few other problems anyone using this pattern will probably encounter, such as overriding related objects' values, and links to other tables, themselves linked. It draws largely from techniques Xelnor introduced in his answer.
class FunctionFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.Function
name = factory.Sequence(lambda n: "Function %d" % n)
class FunctionParameterFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.FunctionParameter
name = factory.Sequence(lambda n: "Function %d" % n)
function = factory.SubFactory(FunctionFactory)
class ParameterSettingFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.ParameterSetting
name = factory.Sequence(lambda n: "Function %d" % n)
function_instantiation = factory.SubFactory(FunctionInstantiationFactory)
function_parameter = factory.SubFactory(FunctionParameterFactory,
function=factory.SelfAttribute('..function_instantiation.function'))
class DatasetAnd2ColumnsFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.Function
dataset = factory.SubFactory(DatasetFactory,
name=factory.Sequence(lambda n: "Custom dataset %d" % n))
column_1 = factory.SubFactory(ColumnFactory, dataset=dataset,
name=factory.Sequence(lambda n: "Column 1 %d" % n))
column_2 = factory.SubFactory(ColumnFactory, dataset=dataset,
name=factory.Sequence(lambda n: "Column 2 %d" % n))
# I found it neater not to inherit in the end, due to needing quite a lot of
# additional complexity not included in my original question.
class FunctionToParameterSettingsFactory(factory.django.DjangoModelFactory):
class Meta:
model = models.FunctionInstantiation
name = factory.Sequence(lambda n: "Custom instantiation name %d" % n)
# You can call Sequence to pass values to SubFactories
function = factory.SubFactory(FunctionFactory,
name=factory.Sequence(lambda n: "Custom function %d" % n))
parameter_setting_1 = factory.RelatedFactory(ParameterSettingFactory,
'function_instantiation',
# Note the __ syntax for override values for nested objects:
parameter__name='Parameter 1',
name='Parameter Setting 1')
# Possible to use Sequence here too, and makes looking at data easier
parameter_setting_2 = factory.RelatedFactory(ParameterSettingFactory,
'function_instantiation',
parameter__name=factory.Sequence(lambda n: "Param 1 for fn %d" % n),
name=factory.Sequence(lambda n: "Param Setting 1 for fn %d" % n))
I now need to create a dataset with some columns of data, and join the parameter_setting records with those columns. To do so, this goes at the end of FunctionToParameterSettingsFactory:
@factory.post_generation
def post(self, create, extracted, **kwargs):
if not create:
return
dataset = DatasetAnd2ColumnsFactory()
column_ids_by_name =
dict((column.name, column.id) for column in dataset.column_set.all())
# self is the `FunctioInstantiation` Django object just created by the `FunctionToParameterSettingsFactory`
for parameter_setting in self.parametersetting_set.all():
if parameter_setting.name == 'age_in':
parameter_setting.column_id = column_ids_by_name['Age']
parameter_setting.save()
elif parameter_setting.name == 'income_in':
parameter_setting.column_id = column_ids_by_name['Income']
parameter_setting.save()
This is admittedly a bit hacky. I tried passing column=column_1 in the RelatedFactory calls, but that triggered creation of multiple datasets, each column linked to a different one. I tried all sorts of acrobatics with SelfAttribute and LazyAttribute, but you can't use either in a RelatedFactory call, and you can't create something with SubFactory(SelfAttribute()) and then pass it into RelatedFactory, as that breaks SelfAttribute (see my other question).
In my real code I had several more models with a foreign key to dataset and it all tied up fine.