Added Manager.get_or_create()

adrianholovaty · adrianholovaty · commit b3a6348bc24d · 2006-06-07T00:09:29.000Z
git-svn-id: https://code.djangoproject.com/svn/django/trunk@3092 bcc190cf-cafb-0310-a4f2-bffc1f526a37
diff --git a/django/db/models/manager.py b/django/db/models/manager.py
@@ -65,6 +65,9 @@ def extra(self, *args, **kwargs):
     def get(self, *args, **kwargs):
         return self.get_query_set().get(*args, **kwargs)
 
+    def get_or_create(self, *args, **kwargs):
+        return self.get_query_set().get_or_create(*args, **kwargs)
+
     def filter(self, *args, **kwargs):
         return self.get_query_set().filter(*args, **kwargs)
 
diff --git a/django/db/models/query.py b/django/db/models/query.py
@@ -205,6 +205,23 @@ def get(self, *args, **kwargs):
         assert len(obj_list) == 1, "get() returned more than one %s -- it returned %s! Lookup parameters were %s" % (self.model._meta.object_name, len(obj_list), kwargs)
         return obj_list[0]
 
+    def get_or_create(self, **kwargs):
+        """
+        Looks up an object with the given kwargs, creating one if necessary.
+        Returns a tuple of (object, created), where created is a boolean
+        specifying whether an object was created.
+        """
+        assert len(kwargs), 'get_or_create() must be passed at least one keyword argument'
+        defaults = kwargs.pop('defaults', {})
+        try:
+            return self.get(**kwargs), False
+        except self.model.DoesNotExist:
+            params = dict([(k, v) for k, v in kwargs.items() if '__' not in k])
+            params.update(defaults)
+            obj = self.model(**params)
+            obj.save()
+            return obj, True
+
     def latest(self, field_name=None):
         """
         Returns the latest object, according to the model's 'get_latest_by'
diff --git a/docs/db-api.txt b/docs/db-api.txt
@@ -705,6 +705,53 @@ The ``DoesNotExist`` exception inherits from
     except ObjectDoesNotExist:
         print "Either the entry or blog doesn't exist."
 
+``get_or_create(**kwargs)``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+A convenience method for looking up an object with the given kwargs, creating
+one if necessary.
+
+Returns a tuple of ``(object, created)``, where ``object`` is the retrieved or
+created object and ``created`` is a boolean specifying whether a new object was
+created.
+
+This is meant as a shortcut to boilerplatish code. For example::
+
+    try:
+        obj = Person.objects.get(first_name='John', last_name='Lennon')
+    except Person.DoesNotExist:
+        obj = Person(first_name='John', last_name='Lennon', birthday=date(1940, 10, 9))
+        obj.save()
+
+This pattern gets quite unwieldy as the number of fields in a model goes up.
+The above example can be rewritten using ``get_or_create()`` like so::
+
+    obj, created = Person.objects.get_or_create(first_name='John', last_name='Lennon',
+                      defaults={'birthday': date(1940, 10, 9)})
+
+Any keyword arguments passed to ``get_or_create()`` -- *except* an optional one
+called ``default`` -- will be used in a ``get()`` call. If an object is found,
+``get_or_create()`` returns a tuple of that object and ``False``. If an object
+is *not* found, ``get_or_create()`` will instantiate and save a new object,
+returning a tuple of the new object and ``True``. The new object will be
+created according to this algorithm::
+
+    defaults = kwargs.pop('defaults', {})
+    params = dict([(k, v) for k, v in kwargs.items() if '__' not in k])
+    params.update(defaults)
+    obj = self.model(**params)
+    obj.save()
+
+In English, that means start with any non-``'defaults'`` keyword argument that
+doesn't contain a double underscore (which would indicate a non-exact lookup).
+Then add the contents of ``defaults``, overriding any keys if necessary, and
+use the result as the keyword arguments to the model class.
+
+Finally, if you have a field named ``defaults`` and want to use it as an exact
+lookup in ``get_or_create()``, just use ``'defaults__exact'``, like so::
+
+    Foo.objects.get_or_create(defaults__exact='bar', defaults={'defaults': 'baz'})
+
 ``count()``
 ~~~~~~~~~~~
 
diff --git a/tests/modeltests/get_or_create/__init__.py b/tests/modeltests/get_or_create/__init__.py
diff --git a/tests/modeltests/get_or_create/models.py b/tests/modeltests/get_or_create/models.py
@@ -0,0 +1,52 @@
+"""
+32. get_or_create()
+
+get_or_create() does what it says: it tries to look up an object with the given
+parameters. If an object isn't found, it creates one with the given parameters.
+"""
+
+from django.db import models
+
+class Person(models.Model):
+    first_name = models.CharField(maxlength=100)
+    last_name = models.CharField(maxlength=100)
+    birthday = models.DateField()
+
+    def __str__(self):
+        return '%s %s' % (self.first_name, self.last_name)
+
+API_TESTS = """
+# Acting as a divine being, create an Person.
+>>> from datetime import date
+>>> p = Person(first_name='John', last_name='Lennon', birthday=date(1940, 10, 9))
+>>> p.save()
+
+# Only one Person is in the database at this point.
+>>> Person.objects.count()
+1
+
+# get_or_create() a person with similar first names.
+>>> p, created = Person.objects.get_or_create(first_name='John', last_name='Lennon', defaults={'birthday': date(1940, 10, 9)})
+
+# get_or_create() didn't have to create an object.
+>>> created
+False
+
+# There's still only one Person in the database.
+>>> Person.objects.count()
+1
+
+# get_or_create() a Person with a different name.
+>>> p, created = Person.objects.get_or_create(first_name='George', last_name='Harrison', defaults={'birthday': date(1943, 2, 25)})
+>>> created
+True
+>>> Person.objects.count()
+2
+
+# If we execute the exact same statement, it won't create a Person.
+>>> p, created = Person.objects.get_or_create(first_name='George', last_name='Harrison', defaults={'birthday': date(1943, 2, 25)})
+>>> created
+False
+>>> Person.objects.count()
+2
+"""
