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Added 'Overriding default model methods' section to model-api.txt

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2955 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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commit 0fc2a2c1a891a9729f99b550bca6334e97c0dce3 1 parent be57a7f
@adrianholovaty adrianholovaty authored
Showing with 34 additions and 1 deletion.
  1. +1 −1  docs/db-api.txt
  2. +33 −0 docs/model-api.txt
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2  docs/db-api.txt
@@ -345,7 +345,7 @@ This is roughly equivalent to::
Entry.objects.order_by('headline')[0:1].get()
-Note, however, that the first of these will raise ``IndexError`` while the
+Note, however, that the first of these will raise ``IndexError`` while the
second will raise ``DoesNotExist`` if no objects match the given criteria.
QuerySet methods that return new QuerySets
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33 docs/model-api.txt
@@ -1599,6 +1599,39 @@ API. See `Other lookup options`_.
.. _Python DB-API: http://www.python.org/peps/pep-0249.html
.. _Other lookup options: http://www.djangoproject.com/documentation/db_api/#extra-params-select-where-tables
+Overriding default model methods
+--------------------------------
+
+As explained in the `database API docs`_, each model gets a few methods
+automatically -- most notably, ``save()`` and ``delete()``. You can override
+these methods to alter behavior.
+
+A classic use-case for overriding the built-in methods is if you want something
+to happen whenever you save an object. For example::
+
+ class Blog(models.Model):
+ name = models.CharField(maxlength=100)
+ tagline = models.TextField()
+
+ def save(self):
+ do_something()
+ super(Blog, self).save() # Call the "real" save() method.
+ do_something_else()
+
+You can also prevent saving::
+
+ class Blog(models.Model):
+ name = models.CharField(maxlength=100)
+ tagline = models.TextField()
+
+ def save(self):
+ if self.name == "Yoko Ono's blog":
+ return # Yoko shall never have her own blog!
+ else:
+ super(Blog, self).save() # Call the "real" save() method.
+
+.. _database API docs: http://www.djangoproject.com/documentation/db_api/
+
Models across files
===================
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