Changeset 2955

Timestamp:

05/21/06 22:01:02 (2 years ago)

Author:

adrian

Message:

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

Files:

• django/trunk/docs/db-api.txt (modified) (1 diff)
• django/trunk/docs/model-api.txt (modified) (1 diff)

django/trunk/docs/db-api.txt

@@ -346 +346 @@
-    Entry.objects.order_by('headline')[0:1].get()
-
- 
+
-second will raise ``DoesNotExist`` if no objects match the given criteria.
-

django/trunk/docs/model-api.txt

@@ -1600 +1600 @@
-.. _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
-===================