从多对多关系的查询 [英] Queryset from a ManyToMany relation

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()

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