ormar/docs/api/models/helpers/relations.md

models.helpers.relations

register_relation_on_build

register_relation_on_build(new_model: Type["Model"], field_name: str) -> None

Registers ForeignKey relation in alias_manager to set a table_prefix. Registration include also reverse relation side to be able to join both sides.

Relation is registered by model name and relation field name to allow for multiple relations between two Models that needs to have different aliases for proper sql joins.

Arguments:

• new_model (Model class): constructed model
• field_name (str): name of the related field

register_many_to_many_relation_on_build

register_many_to_many_relation_on_build(new_model: Type["Model"], field: Type[ManyToManyField], field_name: str) -> None

Registers connection between through model and both sides of the m2m relation. Registration include also reverse relation side to be able to join both sides.

Relation is registered by model name and relation field name to allow for multiple relations between two Models that needs to have different aliases for proper sql joins.

By default relation name is a model.name.lower().

Arguments:

• field_name (str): name of the relation key
• new_model (Model class): model on which m2m field is declared
• field (ManyToManyField class): relation field

expand_reverse_relationships

expand_reverse_relationships(model: Type["Model"]) -> None

Iterates through model_fields of given model and verifies if all reverse relation have been populated on related models.

If the reverse relation has not been set before it's set here.

Arguments:

• model (Model class): model on which relation should be checked and registered

register_reverse_model_fields

register_reverse_model_fields(model: Type["Model"], child: Type["Model"], related_name: str, model_field: Type["ForeignKeyField"]) -> None

Registers reverse ForeignKey field on related model. By default it's name.lower()+'s' of the model on which relation is defined.

But if the related_model name is provided it's registered with that name. Autogenerated reverse fields also set related_name to the original field name.

Arguments:

• model (Model class): related model on which reverse field should be defined
• child (Model class): parent model with relation definition
• related_name (str): name by which reverse key should be registered
• model_field (relation Field): original relation ForeignKey field

register_relation_in_alias_manager

register_relation_in_alias_manager(new_model: Type["Model"], field: Type[ForeignKeyField], field_name: str) -> None

Registers the relation (and reverse relation) in alias manager. The m2m relations require registration of through model between actual end models of the relation.

Delegates the actual registration to: m2m - register_many_to_many_relation_on_build fk - register_relation_on_build

Arguments:

• new_model (Model class): model on which relation field is declared
• field (ForeignKey or ManyToManyField class): relation field
• field_name (str): name of the relation key

verify_related_name_dont_duplicate

verify_related_name_dont_duplicate(child: Type["Model"], parent_model: Type["Model"], related_name: str) -> None

Verifies whether the used related_name (regardless of the fact if user defined or auto generated) is already used on related model, but is connected with other model than the one that we connect right now.

Raises:

• ModelDefinitionError: if name is already used but lead to different related model

Arguments:

• child (ormar.models.metaclass.ModelMetaclass): related Model class
• parent_model (ormar.models.metaclass.ModelMetaclass): parent Model class
• related_name ():

Returns:

(None): None

reverse_field_not_already_registered

reverse_field_not_already_registered(child: Type["Model"], child_model_name: str, parent_model: Type["Model"]) -> bool

Checks if child is already registered in parents pydantic fields.

Raises:

• ModelDefinitionError: if related name is already used but lead to different related model

Arguments:

• child (ormar.models.metaclass.ModelMetaclass): related Model class
• child_model_name (str): related_name of the child if provided
• parent_model (ormar.models.metaclass.ModelMetaclass): parent Model class

Returns:

(bool): result of the check