Changes between Initial Version and Version 1 of CookBookCategoryDataModel

Timestamp:

Aug 5, 2005, 5:21:14 AM (20 years ago)

Author:

oubiwann

Comment:

--

CookBookCategoryDataModel

@@ +1 @@
+= CookBook - Data Modela =
+
+== Description ==
+I like to have parent/child categories for my documents and weblog entries. I also am a fan of simplicity. This recipe lets you create new categories, and children of categories while providing an intuitively obvious presentation to the user. A parent category of 'Development' with a child category of 'Python' will be display as 'Development :: Python'. Using that example, other data models/content types that utilize this code will have drop-downs in the admin interface with entires of 'Development' and 'Development :: Python'
+
+== Code ==
+{{{
+class Category(meta.Model):
+    verbose_name_plural = 'Categories'
+    module_name = verbose_name_plural.lower()
+    fields = (
+        meta.CharField('category_name', maxlength=50),
+        meta.CharField('category_parents', maxlength=250, editable=False),
+        meta.ForeignKey('self', blank=True, null=True, 
+            rel_name='parent', related_name='child'),
+    )
+    unique_together = (("category_name", "category_parents"),)
+
+    def _recurse_for_parents(self, cat_obj):
+        p_list = []
+        if cat_obj.parent_id:
+            p = cat_obj.get_parent()
+            p_list.append(p.category_name)
+            more = self._recurse_for_parents(p)
+            p_list.extend(more)
+        if p_list:
+            p_list.reverse()
+        return p_list
+
+    def get_separator(self):
+        return ' :: '
+
+    def _parents_repr(self):
+        p_list = self._recurse_for_parents(self)
+        return self.get_separator().join(p_list)
+
+    def __repr__(self):
+        if self.category_parents:
+            l = [self.category_parents, self.category_name]
+            return self.get_separator().join(l)
+        return self.category_name
+
+    def _pre_save(self):
+        self.category_parents = self._parents_repr()
+
+    admin = meta.Admin(
+        list_display = ('category_name', 'category_parents'),
+        search_fields = ['category_name', 'category_parents'],
+    )
+    ordering = ('category_parents', 'category_name')
+}}}
+
+== API Usage ==
+Let's fill in some root-level categories:
+{{{
+>>> from yourpkg.apps.yourapp.models import yourapp
+>>> base_cats = [
+...   {'category_name': 'Development'},
+...   {'category_name': 'Systems'},
+...   {'category_name': 'Management'},
+...   {'category_name': 'Community'},
+... ]
+>>> for cat in base_cats:
+...   new_cat = yourapp.Category(**cat)
+...   new_cat.save()
+>>>
+}}}
+
+Now, let's create some sub categories, examining the dict as we go:
+{{{
+>>> cat = {'parent_id': 1, 'category_name': 'Python'}
+>>> new_cat = yourapp.Category(**cat)
+>>> new_cat.__dict__
+{'parent_id': 1, 'id': '', 'category_parents': '', 'category_name': 'Python'}
+>>> new_cat._pre_save()
+>>> new_cat.__dict__
+{'_parent_cache': Development, 'parent_id': 1, 'id': '', 'category_parents': 'Development', 'category_name': 'Python'}
+>>> new_cat.save()
+>>> new_cat.__dict__
+{'_parent_cache': Development, 'parent_id': 1, 'id': 5, 'category_parents': 'Development', 'category_name': 'Python'}
+>>> new_cat
+Development :: Python
+}}}
+
+
+Now, let's add a few more and print all the categories:
+{{{
+>>> cat = {'parent_id': 2, 'category_name': 'Administration'}
+>>> yourapp.Category(**cat).save()
+>>> cat = {'parent_id': 7, 'category_name': 'UNIX'}
+>>> yourapp.Category(**cat).save()
+>>> for cat in yourapp.categories.get_list():
+...   print cat
+... 
+Community
+Development
+Management
+Systems
+Development :: Python
+Systems :: Administration
+Systems :: Administration :: UNIX
+}}}
+== Usage in Other Data Models ==
+{{{
+class Document(meta.Model):
+    fields = (
+        meta.CharField('title', maxlength=200),
+        meta.ForeignKey(Category, name='subject', blank=True, null=True),
+        ...
+}}}