与Django建立一对多关系 [英] Create a one to many relationship with Django

问题描述

伙计们，我正在制作一个社交媒体应用程序，我有一个用户表，其中使用了Django的通用用户模型.

Hey guys I'm making a social media app and I have a User table with the generic User Model from Django used.

我现在正在创建一个关注表，我想在其中跟踪用户关注的不同用户名以及关注他的用户数(我不需要显示关注者字段的名称，而只需显示关注者的数量用户拥有).

I'm now creating a Follow table where I want to keep track of the different usernames the user follows and a count of those following him (I don't need to display the names for the followers field just the amount of followers a user has).

我将如何去做?现在，这就是我所拥有的，但是我无法查看数据库中的实际数据，因此不确定其工作方式.是否有从用户模型借用的用户名列?我找不到有关其工作原理的可靠信息.

How would I go about doing this? Right now this is what I have, but I'm unable to view the actual data in the database so I'm not sure how it works. Is there a column for username that is borrowed from the User model? I can't find solid information on how this works.

    from django.contrib.auth.models import AbstractUser
from django.contrib.postgres.fields import ArrayField
from django.db import models

class User(AbstractUser):
    pass
    
class Follow(models.Model):
    followers = models.IntegerField(default=0)
    following = models.ForeignKey(User, related_name = 'follow_to_set', on_delete = models.CASCADE)

class NewPost(models.Model):
    username = models.CharField(max_length=64)
    body = models.CharField(max_length=64)
    likes = models.IntegerField(default=0)
    timestamp = models.DateTimeField(auto_now_add=True)

推荐答案

您可以尝试以下方式:

models.py

from django.db import models
from django.contrib.auth.models import User

class Profile(models.Model) :
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name = "user_profile")
    followers = models.IntegerField(default=0)

    def __str__(self):
        return self.user.username

class Follow(models.Model):
    follower = models.ForeignKey(Profile, on_delete=models.CASCADE) 
    following = models.ForeignKey(Profile, on_delete=models.CASCADE)
    followed_on = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return f'{self.following} <- {self.follower}'

class NewPost(models.Model):
    username = models.CharField(max_length=64)
    body = models.CharField(max_length=64)
    likes = models.IntegerField(default=0)
    timestamp = models.DateTimeField(auto_now_add=True)

上面的 Follow 模型保存以下记录.

The above Follow model saves the record of the follows.

例如，有两个用户 A 和 B ，因此，如果 A 开始关注 B ，则关注模型将保存一条记录，其中 follower 将为 A ，并且 following 将为 B ，并且 followed_on 是用户 A 在用户 B 之后开始的日期.

For example there are two users A and B so if A starts following B then the Follow model will save a record in that follower will be A and following will be B and the followed_on will be the date when the user A started following user B.

您还可以编写一个信号，以在一个用户关注另一个用户时添加关注者计数.

You can also write a signal for adding the follower count when a user follows another user.

请参见下文

from djano.dispatch import receiver
from django.db.models.signals import post_save

@receiver(post_save, sender=Follow)
def add_follow_count(sender, instance, created, **kwargs):
    try:
        if created:
           user = Profile.objects.get(id=instance.following.id)
           user.followers +=1
           user.save()
    except Exception as e:
        print("Error incrementing follower count.")
        print(e)

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