如何在单个 Django 视图中跨多个模型进行查询？

Question

我目前在我的 Django 代码中有以下模型。

from django.conf import settings  
import math 
from django.contrib.auth import get_user_model
from django.db import models
from django.urls import reverse 
# Create your models here.
import statistics 
from django.utils import timezone  
from decimal import Decimal 
#import for mail
from django.core.mail import EmailMessage, send_mail
from django.db.models import Q, QuerySet, F, FloatField, ExpressionWrapper, Manager 
from django.db.models.functions import Cast 
from django.db.models.aggregates import Avg
import datetime 
from django.utils import timezone

class Card(models.Model):
    card_name = models.CharField(max_length=255)

    geography_choices = [('Africa', 'Africa'), ('Asia', 'Asia'), ('Australia', 'Australia'), ('Europe', 'Europe'), ('North America', 'North America'), ('South America', 'South America')]
    geography = models.CharField(max_length=255, choices=geography_choices, default='North America')

    type_choices = [('Creature', 'Creature'), ('Spell', 'Spell'), ('New Type', 'New Type'),('Undecided', 'Undecided')]
    card_type = models.CharField(max_length=255, choices=type_choices, default='Creature')


class Article(models.Model):

    title = models.CharField(max_length=255)

    body = models.TextField()

    author = models.ForeignKey(
        get_user_model(),
        on_delete=models.CASCADE, 
    )

    entry_date_time = models.DateTimeField(default=timezone.now, null=True)

    class Meta:
        ordering = ['-entry_date_time']

    score_choices = [(-5,'-5'), (-4, '-4'), (-3,'-3'), (-2, '-2'), (-1,'-1'), (0,'0'),
    (1,'1'), (2,'2'), (3,'3'), (4,'4'), (5,'5')]
    score = models.FloatField(choices=score_choices, default=0)


    read_through_choices = [(-1, 'Competitive'), (0, 'No Effect'), (1, 'Industry-Wide')]
    read_through = models.IntegerField(choices=read_through_choices, default=0)


    cardvar = models.ForeignKey(Card, on_delete=models.CASCADE, null=True)

我正在尝试运行搜索我的文章的搜索功能，并且 a) 返回“cardvar__card_name”与我们的查询匹配的文章，以及 b)“cardvar__card_type”与我们的查询类型匹配的文章（我们的查询只是一个 cardvar__card_name）以及“分数”不等于零。

我能够单独完成 a) 部分而没有问题，但是，当我尝试实施 BI 部分时，最终得到服务器错误 500。我认为这是因为我在同一视图中同时拥有 Equity 和 Article 模型。 但是，我完全不知道如何解决这个问题。 任何帮助将不胜感激。

class SearchResultsListView(ListView): #new
    model = Article
    context_object_name = 'article_list'
    template_name = 'search_results.html'
    def get_queryset(self):
       query =self.request.GET.get('q')
       card_dict = Card.objects.values('card_type').get(card_name=query)
       results = Article.objects.filter(
        Q(cardvar__card_name__iexact=query) | 
       (Q(cardvar__card_type=card_dict['card_type'] & 
       ~Q(score=0))
       ).order_by('cardvar', '-entry_date_time')
    return results

Answer 1

您在第二个Q()处缺少括号。

并且您需要捕获可能的DoesNotExist异常。 尝试这个：

class SearchResultsListView(ListView): #new
    model = Article
    context_object_name = 'article_list'
    template_name = 'search_results.html'

    def get_queryset(self):
       query = self.request.GET.get('q')
       try:
           card_dict = Card.objects.values('card_type').get(card_name=query)
           results = Article.objects.filter(Q(cardvar__card_name__iexact=query) |
                        (Q(cardvar__card_type=card_dict['card_type']) & 
                        ~Q(score=0))).order_by('cardvar', '-entry_date_time')
       except Card.DoesNotExist:
            results = Article.objects.filter(Q(cardvar__card_name__iexact=query)
                         ).order_by('cardvar', '-entry_date_time')
       return results