SingletonModel

The SingletonModel is an abstract model that provides functionality for only allowing a single instance of a model to be created. It includes the following field:

• singleton_id: A PositiveIntegerField that stores the ID of the singleton instance. This field should always have a value of 1.

The SingletonModel also includes a custom save method that overrides the default behavior to prevent multiple instances from being created. It also includes a load method that returns the singleton instance of the model.

class core.models.SingletonModel(*args, **kwargs)

Abstract model that provides functionality for only

allowing a single instance of a model to be created.

singleton_id

A field that stores the ID of the singleton instance. This field should always have a value of 1.

Type:

PositiveIntegerField

clean()

Hook for doing any extra model-wide validation after clean() has been called on every field by self.clean_fields. Any ValidationError raised by this method will not be associated with a particular field; it will have a special-case association with the field defined by NON_FIELD_ERRORS.

clean_fields(exclude=None)

Clean all fields and raise a ValidationError containing a dict of all validation errors if any occur.

full_clean(exclude=None, validate_unique=True)

Call clean_fields(), clean(), and validate_unique() on the model. Raise a ValidationError for any errors that occur.

get_deferred_fields()

Return a set containing names of deferred fields for this instance.

classmethod load()

Returns the singleton instance of the model.

Creates the instance if it does not exist yet.

refresh_from_db(using=None, fields=None)

Reload field values from the database.

By default, the reloading happens from the database this instance was loaded from, or by the read router if this instance wasn’t loaded from any database. The using parameter will override the default.

Fields can be used to specify which fields to reload. The fields should be an iterable of field attnames. If fields is None, then all non-deferred fields are reloaded.

When accessing deferred fields of an instance, the deferred loading of the field will call this method.

save(*args, **kwargs)

Overrides the save method to prevent multiple

instances from being created.

save_base(raw=False, force_insert=False, force_update=False, using=None, update_fields=None)

Handle the parts of saving which should be done only once per save, yet need to be done in raw saves, too. This includes some sanity checks and signal sending.

The ‘raw’ argument is telling save_base not to save any parent models and not to do any changes to the values before save. This is used by fixture loading.

serializable_value(field_name)

Return the value of the field name for this instance. If the field is a foreign key, return the id value instead of the object. If there’s no Field object with this name on the model, return the model attribute’s value.

Used to serialize a field’s value (in the serializer, or form output, for example). Normally, you would just access the attribute directly and not use this method.

validate_unique(exclude=None)

Check unique constraints on the model and raise ValidationError if any failed.