没有自动列出的类似问题回答我的问题：
我有models.py如下：
```from django.db import models
class Location(models.Model):
name = models.CharField(max_length=200)
address = models.CharField(max_length=300)
def __str__(self):
return f'{self.name} ({self.address})'
class Participant(models.Model):
email = models.EmailField(unique=True)
def __str__(self):
return self.email
class Meetup(models.Model):
title = models.CharField(max_length=200)
slug = models.SlugField(unique=True)
description = models.TextField()
image = models.ImageField(upload_to='images')
location = models.ForeignKey(Location, on_delete=models.CASCADE)
participants = models.ManyToManyField(Participant)
def __str__(self):
return f'{self.title} - {self.slug} - {self.description}'```为了能够列出我通过管理面板输入的两封电子邮件，我有以下Admin.py
```from django.contrib import admin
from .models import Meetup, Location, Participant
# Register your models here.
class MeetupAdmin(admin.ModelAdmin):
list_display = ('title', 'slug', 'description', 'location', 'get_emails')
def get_emails(self, obj):
return "\n".join([p.email for p in obj.participants.all()])
list_filter = ('title', 'description')
prepopulated_fields = {'slug': ('title', )}
search_fields = ('title', )
admin.site.register(Meetup, MeetupAdmin)
admin.site.register(Location)
admin.site.register(Participant)```不使用函数
return "\n".join([p.email for p in obj.participants.all()])```
I would not have been able to list the two emails represented by the ManyToMany relation
My question here is: I would like to understand what does the p and obj here. I would be so grateful if someone could explain how this work.
1条答案
按热度按时间5lwkijsr1#
您可以在
list_display中传递方法的名称，在这种情况下，对于ModelAdmin将显示的每个记录，它将调用带有obj的函数，该对象是它想要呈现内容的对象。这里
obj是一个Meetup对象，你可以访问一个ManyToManyField，所以obj.participants.all()将返回所有链接到Meetup的Participant。我们在这里使用列表解析来生成一个.emails的列表，然后使用'\n'.join(…)来创建一个字符串，我们用新行（'\n'）分隔电子邮件地址。但是，这并不是很有效：如果
Meetup的数量将增长，这将导致大量的查询。您可以使用以下命令在 one extra query中选择所有相关的Participant：