Django过滤模型在ManyToMany数？ [英] Django filter the model on ManyToMany count?

问题描述

假设我的models.py有这样的东西：

  class Hipster（models.Model）：
 name = CharField（max_length = 50）
 
 class Party（models.Model）：
 organizer = models.ForeignKey（）
 Particip = models.ManyToManyField（Profile，related_name = 参与者）
  

现在在我的views.py中，我想做一个查询，有超过0位参与者的用户聚会。

这样做可能：

  user = Hipster.get pk = 1）
 hip_parties = Party.objects.filter（organizer = user，len（Participants）> 0）
  

最好的做法是什么？

解决方案

如果这样工作，这是怎么做到的。最好的方法可以意味着很多事情最好的表现，最可维护的等等。所以我不会说这是最好的方法。但是，我喜欢尽可能多地遵守ORM功能，因为它似乎更易于维护。

 从django.db.models导入计数
 user = Hipster.get（pk = 1）
 hip_parties = Party.objects.annotate（num_participants = Count（'participant'））\ 
 .filter（organizer = user，num_participants__gt = 0）
  

Suppose I have something like this in my models.py:

class Hipster(models.Model):
  name = CharField(max_length=50)

class Party(models.Model):
  organiser = models.ForeignKey()
  participants = models.ManyToManyField(Profile, related_name="participants")

Now in my views.py I would like to do a query which would fetch a party for the user where there are more than 0 participants.

Something like this maybe:

user = Hipster.get(pk=1) 
hip_parties = Party.objects.filter(organiser=user, len(participants) > 0)

What's the best way of doing it?

解决方案

If this works this is how I would do it. Best way can mean a lot of things best performance, most maintainable, etc. Therefor I will not say this is the best way. However I like to stick to the ORM features as much as possible since it seems more maintainable.

from django.db.models import Count
user = Hipster.get(pk=1) 
hip_parties = Party.objects.annotate(num_participants=Count('participants')) \
    .filter(organiser=user, num_participants__gt=0)

这篇关于Django过滤模型在ManyToMany数？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！