在 django 模板中使用聚合 QuerySet 中的字段
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【中文标题】在 django 模板中使用聚合 QuerySet 中的字段【英文标题】：Using fields from a aggregated QuerySet in a django template 【发布时间】：2021-10-13 19:10:48 【问题描述】：所以我从一个聚合函数中获得了一个 QuerySet 结果，以显示在我的低规格 eBay 克隆中。但我的问题是根据需要在 Django 模板中显示某些字段，例如，我想显示最高出价者的用户名和出价。当我像winner 那样调用整个对象本身时，它就会显示出来。但是当我尝试像winner.user_id.username 那样访问它的字段时，尽管 QuerySet 确实执行了，但我没有得到任何输出。
当我尝试获取这样的字段时 (winner.user_id.username)：
当我只打电话给winner时：
models.py
from django.contrib.auth.models import AbstractUser
from django.db import models
CATEGORIES = [
('Appliances', 'Appliances'),
('Tech', 'Tech'),
('Gaming', 'Gaming'),
('Fashion', 'Fashion'),
('Sports and Fitness','Sports and Fitness'),
('Other','Other'),
("Hygiene and Medicine","Hygiene and Medicine"),
("Stationery","Stationery"),
('Decor', 'Decor'),
('Furniture','Furniture'),
('Cars and Mechanical Things','Cars and Mechanical Things'),
("Tools","Tools")
]
# Create models here
class User(AbstractUser):
pass
class Auction_Listing(models.Model):
user_id = models.IntegerField(default=1)
list_title = models.CharField(max_length=64)
desc = models.TextField(max_length=600)
img_url = models.URLField(max_length=200, null=True, blank=True)
start_bid = models.IntegerField()
category = models.CharField(choices=CATEGORIES, max_length=35, null=True, blank=True)
active = models.BooleanField(default=True)
def __str__(self):
return f"ID:self.id, self.list_title: self.desc, self.start_bid posted by user:self.user_id in Category:self.category, url:self.img_url"
class Bids(models.Model):
user_id = models.ForeignKey('User', on_delete=models.CASCADE)
auctions = models.ForeignKey('Auction_Listing', on_delete=models.CASCADE, default=1,related_name='bidauc')
bid = models.IntegerField()
def __str__(self):
return f"ID:self.id, Bid self.bid posted by user:self.user_id on auction self.auctions"
class Auction_Comments(models.Model):
user_id = models.ForeignKey('User', on_delete=models.CASCADE)
comment = models.TextField(max_length=324, default='N/A')
auctions = models.ForeignKey('Auction_Listing', on_delete=models.CASCADE, default=1,related_name='comauc')
def __str__(self):
return f"ID:self.id, Comment: self.comment posted by user:self.user_id on auction self.auctions"
class Watchlist(models.Model):
user_id = models.ForeignKey('User', on_delete=models.CASCADE)
auctions = models.ForeignKey('Auction_Listing', on_delete=models.CASCADE, default=1, related_name='watchauc')
def __str__(self):
return f"ID:self.id, user:self.user_id on auction self.auctions"
views.py
def render_listing(request, title):
if request.method == "POST":
form = BidForm(request.POST)
bid = int(request.POST['new_bid'])
listing = Auction_Listing.objects.get(list_title=title)
comments = Auction_Comments.objects.filter(auctions=listing)
if bid <= listing.start_bid:
error = True
else:
error = False
listing.start_bid = bid
listing.save()
new_bid = Bids(user_id=request.user, auctions=listing, bid=bid)
new_bid.save()
return render(request, 'auctions/listing.html',
"listing": listing,
"form": form,
"comments": comments,
"error": error,
"comform": CommentForm()
)
else:
form = BidForm()
comform = CommentForm()
listing = Auction_Listing.objects.get(list_title=title)
comments = Auction_Comments.objects.filter(auctions=listing)
high_bid = Bids.objects.filter(auctions=listing).aggregate(maximum=Max("bid"))
winner = Bids.objects.filter(auctions=listing, bid=high_bid['maximum'])
print(winner)
return render(request, 'auctions/listing.html',
"listing": listing,
"form": form,
"comments": comments,
"error": False,
"comform": comform,
"winner": winner
)
模板代码：
% extends "auctions/layout.html" %
% load static %
% block title % Listing: listing.list_title % endblock %
% block body %
% if listing.active %
<h2> listing.list_title </h2>
<div class='listing'>
% if listing.img_url == "" or listing.img_url == None %
<a href='#'><img src="% static 'auctions/img404.png' %" class='img-fluid'></a>
% else %
<a href='#'><img src=" listing.img_url " class="img-fluid" alt='image of listing.list_title '></a>
% endif %
<p>
listing.desc
</p>
<p>
Current Bid: $ listing.start_bid
</p>
<p>Category: listing.category </p>
<p></p>
% if user.is_authenticated %
<div class="bid">
<a href='% url "watch" listing.list_title %' class='btn btn-primary'>Add to/Remove from Watchlist</a>
% if listing.user_id == user.id %
<a href='% url "close" listing.list_title %' class='btn btn-primary'>Close Auction</a>
% endif %
</div>
<div class="bid">
<h3>Bid:</h3>
<form method="POST" action='% url "renlist" listing.list_title %'>
% csrf_token %
form
<button type="submit" class='btn btn-primary'>Make New Bid</button>
% if error %
Please enter a bid higher than the current bid.
% endif %
</form>
</div>
% else %
<p><a href='% url "register" %' class='register'>Register</a> to bid on this item and gain access to other features</p>
% endif %
</div>
<div class="listing">
<h3>Comments:</h3>
% if user.is_authenticated %
<div id='comform'>
<h4>Post a Comment</h4>
<form method="POST" action="% url 'commentadd' %">
% csrf_token %
comform
<button type="submit" class="btn btn-primary">Post Comment</a>
</form>
</div>
% endif %
<p>
% for comment in comments %
<div class="comment">
<h4>comment.user_id.username posted:</h4>
<p>comment.comment</p>
</div>
% empty %
<h4>No comments as of yet</h4>
% endfor %
</p>
</div>
% else %
<h2>This auction has been closed</h2>
<div>
<a href='% url "watch" listing.list_title %' class='btn btn-primary'>Add to/Remove from Watchlist</a>
</div>
<p>winner.user_id.username</p>
% endif %
% endblock %
提前感谢您的帮助！ 亲切的问候 PrimeBeat
【问题讨论】：
【参考方案1】：这将给出一个QuerySet。 您可以在第二张图片中看到。
QuerySet 代表数据库中对象的集合。
winner = Bids.objects.filter(auctions=listing, bid=high_bid['maximum'])
您需要遍历该 QuerySet，获取所需的任何数据并将其显示在模板中。
% for win in winner %
<p> win.user_id.username </p>
% endfor %
【讨论】：
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