Django项目点击view按钮报MultiValueDictKeyError 'bid'错误求助

问题根因 #

• 点击View按钮访问页面是GET请求，你的viewList视图没有区分GET/POST请求，if not listing.activate:分支下的逻辑会在所有请求类型下执行，GET请求的request.POST为空，直接用request.POST['bid']取值找不到对应键就抛出MultiValueDictKeyError
• 同时代码还存在多个字段不匹配、表单缺失的问题，会导致后续功能异常：
  • 视图里判断出价高低用了不存在的listing.startBid字段，Post模型对应字段是price/currentBid
  • 模板item.html里判断创建者用了listing.owner，Post模型对应字段是listing.creator
  • item.html缺少出价表单，用户无法提交bid参数

修复方案 #

1. 修正views.py的viewList视图 #

def viewList(request, id):
    # check for the watchlist
    listing = Post.objects.get(id=id)
    user = request.user # 无需二次查询User，request.user本身就是User对象
    if listing.watchers.filter(id=request.user.id).exists():
        is_watched = True
    else:
        is_watched = False

    # 仅处理POST请求
    if request.method == "POST":
        if not listing.activate:
            if request.POST.get('button') == "Close":
                listing.activate = True
                listing.save()
            else:
                # 用get取值避免KeyError，取不到就返回错误提示
                bid_value = request.POST.get('bid')
                if not bid_value:
                    return render(request, 'auctions/item.html', {
                        "listing": listing,
                        'form': BidForm(),
                        "message": "请输入出价金额",
                        "is_watched": is_watched
                    })
                price = float(bid_value)
                bids = listing.bids.all()
                if user.username != listing.creator.username:
                    # 修正字段名，判断价格要大于当前最高价/起拍价
                    min_bid = listing.currentBid if listing.currentBid else listing.price
                    if price <= min_bid:
                        return render(request, 'auctions/item.html', {
                            "listing": listing,
                            'form': BidForm(),
                            "message": "错误！您的出价必须高于当前报价！",
                            "is_watched": is_watched
                        })
                    form = BidForm(request.POST)
                    if form.is_valid():
                        bid = form.save(commit=False)
                        bid.user = user
                        bid.save()
                        listing.bids.add(bid)
                        listing.currentBid = price # 修正字段名，存到currentBid
                        listing.save()
                    else:
                        return render(request, 'auctions/item.html', {
                            "form": BidForm(),
                            "listing": listing,
                            "is_watched": is_watched
                        })
        return HttpResponseRedirect(reverse('viewList', args=(listing.id,)))
    
    context = {
        'listing': listing,
        'comment_form': CommentForm(),
        'comments': listing.get_comments.all(),
        'is_watched': is_watched,
        'form': BidForm()
    }
    return render(request, 'auctions/item.html', context)

2. 修正item.html模板 #

在出价区域补充出价表单，同时修正创建者判断的字段名：

<div class="newbid">
    <p>{{ message }}</p>
    {% if listing.activate %}
    <li><strong>中标者：</strong>{{ listing.bids.last.user.username }}</li>
    {% endif %}

    {% if user.username == listing.creator.username and not listing.activate %}
    <form action="{% url 'viewList' listing.id %}" method="POST" class="mb-3">
        {% csrf_token %}
        <button type="submit" name="button" class="btn btn-danger" value="Close">关闭竞价</button>
    </form>
    {% endif %}

    <!-- 补充出价表单 -->
    {% if not listing.activate and user.username != listing.creator.username %}
    <form action="{% url 'viewList' listing.id %}" method="POST">
        {% csrf_token %}
        {{ form.as_p }}
        <button type="submit" class="btn btn-primary mt-2">提交出价</button>
    </form>
    {% endif %}
</div>

内容的提问来源于stack exchange，提问作者wajd