This code will generate a model that has a nice interface for people
constructing sites organized around hierarchical menus. When adding a
page, the current structure of the site shows up like this:
root node
-child node
--child of a child node
If a loop is detected during insertion, the page is moved to the root
of the hierarchy. The code is probably terribly inefficient. I
couldn't get the preorder traversal tree working to save my life, so
I devised this. Let me know what you think.
Dan
from django.db import models, connection
from django.db.models.query import Q
import pprint
weight_options = []
for item in range(-10,11):
weight_options.append([item, item])
class Page(models.Model):
parent = models.ForeignKey('self', null=True, blank=True)
title = models.CharField(maxlength=100, core=True)
slug = models.SlugField(help_text='Friendly URL', unique=True,
prepopulate_from=('title',))
alias = models.CharField(blank=True, maxlength=100)
weight = models.IntegerField(help_text='Lower weights show up
earlier in lists. If items have the same weight, they are sorted by
name.', default=0, choices=weight_options)
body = models.TextField(blank=True, null=True)
created = models.DateTimeField('Date Created', auto_now_add=True)
modified = models.DateTimeField('Date Last Modified', auto_now=True)
index = models.IntegerField(default=0, help_text='This field is
used internally to properly arrange the menu. Please do not edit this
field.')
depth = models.IntegerField(default=0, help_text='This field is
used to format the menu. Please do not edit this field.')
class Admin:
fields = (
('Page', { 'fields' : ('title', 'body',) }),
('Menu', { 'fields' : ('parent', 'weight',) }),
('Advanced', { 'fields': ('slug', 'alias', 'index',
'depth',) , 'classes': 'collapse' }),
)
list_display=('__str__', 'admin_links', 'created', 'modified',)
list_filter=('modified', 'created',)
search_fields=('title', 'body',)
ordering=('index',)
class Meta:
ordering = ('index',)
def get_absolute_url(self):
if self.alias:
return self.alias
else:
return '/pages/%s' % self.slug
def admin_links(self):
return '<a href="%s">edit</a> | <a href="%s">view</a> | <a
href="%s/delete">delete</a>' % (self.id, self.get_absolute_url(),
self.id)
admin_links.allow_tags = True
admin_links.short_description = 'Actions'
def __str__(self):
return '-' * self.depth + self.title
def ancestors(self):
list = []
page = self
while page:
if page in list:
raise 'loop detected'
list.append(page)
page = page.parent
return list
def save(self):
super(Page, self).save()
# Make sure there are no loops in the hierarchy
try:
self.ancestors()
except:
self.parent = None
# Call the super's save, so that the DB is correct before we
modify it.
super(Page, self).save()
def get_order_recurse(parent, depth, index):
pages = Page.objects.filter(parent=parent).order_by('weight')
for page in pages:
page.index = index
page.depth = depth
super(Page, page).save()
index = get_order_recurse(page, depth + 1, index + 1)
return index
index = 0
pages = Page.objects.filter(parent__isnull=True).order_by('weight')
for page in pages:
page.index = index
page.depth = 0
super(Page, page).save()
index = get_order_recurse(page, 1, index + 1)
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