从多对多关系的查询

本文介绍了从多对多关系的查询的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 我正在Django创建一个小日历应用程序。我有两个模型类;日历和事件。事件可以在多个日历中。因为这样我使用了一个ManyToMany关系。

这是我的模型

from django.db import models class Calendar（models.Model）： title = models.CharField（max_length = 255） def __unicode__ （self）： return self.title class Event（models.Model）： title = models.CharField（max_length = 255） start_date = models。 DateField（） end_date = models.DateField（blank = True，null = True） location = models.CharField（blank = True，max_length = 255） description = models.TextField = True） important = models.BooleanField（default = False） calendar = models.ManyToManyField（Calendar）

如何从特定日历中获取所有事件的查询器？

解决方案

日历记录实例上的.event_set属性。像这样：

＃创建两个日历 one = models.Calendar.objects.create（title ='calendar one '） two = models.Calendar.objects.create（title ='calendar two'） ＃将事件1连接到两个日历 event = models.Event.objects。 create（title ='event 1'，start_date ='2011-11-11'） one.event_set.add（event） two.event_set.add（event） ＃attach event 2 to calendar 2 two.event_set.add（models.Event.objects.create（title ='event 2'，start_date ='2011-11-11'）） ＃获取并打印日历中的所有事件 events_one = models.Calendar.objects.get（title ='calendar one'）。event_set.all（） print [event.title for event in event_one] ＃将打印：[u'event 1'] ＃从日历2获取并打印所有事件 events_two = models.Calendar.objects.get（title = 'calendar two'）。event_set.all（） print [event.title for event in events_two] ＃将打印：[u'event 1' ，u'event 2']

models.Calendar.objects.get（title ='two'） .event_set.all（）

I'm creating a little calendar app in Django. I have two model classes; Calendar and Event. An event can be in multiple calendars. Because of this I'm using a ManyToMany relation.

This is my model

from django.db import models class Calendar(models.Model): title = models.CharField(max_length = 255) def __unicode__(self): return self.title class Event(models.Model): title = models.CharField(max_length = 255) start_date = models.DateField() end_date = models.DateField(blank = True, null = True) location = models.CharField(blank = True, max_length = 255) description = models.TextField(blank = True) important = models.BooleanField(default = False) calendar = models.ManyToManyField(Calendar)

How can I get a queryset with all events from a specific calendar?

解决方案

You would use the .event_set attribute on an instance of a Calendar record. Like this:

# create two calendars one = models.Calendar.objects.create(title='calendar one') two = models.Calendar.objects.create(title='calendar two') # attach event 1 to both calendars event = models.Event.objects.create(title='event 1', start_date='2011-11-11') one.event_set.add(event) two.event_set.add(event) # attach event 2 to calendar 2 two.event_set.add(models.Event.objects.create(title='event 2', start_date='2011-11-11')) # get and print all events from calendar one events_one = models.Calendar.objects.get(title='calendar one').event_set.all() print [ event.title for event in events_one ] # will print: [u'event 1'] # get and print all events from calendar two events_two = models.Calendar.objects.get(title='calendar two').event_set.all() print [ event.title for event in events_two ] # will print: [u'event 1', u'event 2']

models.Calendar.objects.get(title='two').event_set.all()