where does "create()" method comes from in django - django

Question

I just want to know where create method comes from in django.
I checked Model class, BaseManager class and so on.
I cannot find where create method is defined.
Anyone knows about it ?
https://github.com/django/django/blob/2d6179c819010f6a9d00835d5893c4593c0b85a0/django/

Answer 1

Short answer: In the QuerySet class.
This is defined in the QuerySet. Indeed, in the Manager, it is wrapped to the QuerySet source [GitHub]:
#classmethod
def _get_queryset_methods(cls, queryset_class):
def create_method(name, method):
def manager_method(self, *args, **kwargs):
return getattr(self.get_queryset(), name)(*args, **kwargs)
manager_method.__name__ = method.__name__
manager_method.__doc__ = method.__doc__
return manager_method
new_methods = {}
for name, method in inspect.getmembers(queryset_class, predicate=inspect.isfunction):
# Only copy missing methods.
if hasattr(cls, name):
continue
# Only copy public methods or methods with the attribute `queryset_only=False`.
queryset_only = getattr(method, 'queryset_only', None)
if queryset_only or (queryset_only is None and name.startswith('_')):
continue
# Copy the method onto the manager.
new_methods[name] = create_method(name, method)
return new_methods
The _get_queryset_methods is called when constructing the Manager class [GitHub]:
class Manager(BaseManager.from_queryset(QuerySet)):
pass
and the from_queryset will attach the QuerySet methods to the Manager class [GitHub]:
#classmethod
def from_queryset(cls, queryset_class, class_name=None):
if class_name is None:
class_name = '%sFrom%s' % (cls.__name__, queryset_class.__name__)
return type(class_name, (cls,), {
'_queryset_class': queryset_class,
**cls._get_queryset_methods(queryset_class),
})
This is done to implement for each method in the QuerySet a method in the Manager to prevent implementing the same logic multiple times. If you thus call .create on the .objects manager (or any other manager), it will call .get_queryset(), and then call that method (here create) on the given QuerySet that get_queryset returns.
The QuerySet thus has a method create that is implemented as [GitHub]:
def create(self, **kwargs):
"""
Create a new object with the given kwargs, saving it to the database
and returning the created object.
"""
obj = self.model(**kwargs)
self._for_write = True
obj.save(force_insert=True, using=self.db)
return obj