django-mptt学习

Simple registration of models - fields required for tree structure will be added automatically.
The tree structure is automatically updated when you create or delete model instances, or change an instance's parent.
Each level of the tree is automatically sorted by a field (or fields) of your choice.
New model methods are added to each registered model for:
    changing position in the tree
    retrieving ancestors, siblings, descendants
    counting descendants
    other tree-related operations
A TreeManager manager is added to all registered models. This provides methods to:
    move nodes around a tree, or into a different tree
    insert a node anywhere in a tree
    rebuild the MPTT fields for the tree (useful when you do bulk updates outside of django)
Form fields for tree models.
Utility functions for tree models.
Template tags and filters for rendering trees.
Admin classes for visualizing and modifying trees in Django's administration interface.

from django.db import models
from mptt.models import MPTTModel, TreeForeignKey

class Genre(MPTTModel):
    name = models.CharField(max_length=50, unique=True)
    parent = TreeForeignKey('self', null=True, blank=True,related_name='children', db_index=True)
    class MPTTMeta:
        order_insertion_by = ['name']


rock = Genre.objects.create(name="Rock")
blues = Genre.objects.create(name="Blues")
Genre.objects.create(name="Hard Rock", parent=rock)
Genre.objects.create(name="Pop Rock", parent=rock)