UnboundLocalError：在Django中賦值之前引用了局部變量“ form”

Question

所以我正在開發一個Django項目，這是我的views.py文件：

def new_topic(request, pk):
    board = get_object_or_404(Board, pk=pk)
    user = User.objects.first()  # TODO: get the currently logged in user

    if request.method == 'POST':
        form = NewTopicForm(request.POST)
    if form.is_valid():
        topic = form.save()
        return redirect('board_topics', pk=board.pk)
    else:
        form = NewTopicForm()
    return render(request, 'new_topic.html', {'form': form})

運行服務器時，出現錯誤消息：

UnboundLocalError: local variable 'form' referenced before assignment

這是我的new_topic.html文件

{% extends 'base.html' %}

{% block title %}Start a New Topic{% endblock %}

{% block breadcrumb %}
    <li class="breadcrumb-item"><a href="{% url 'home' %}">Boards</a></li>
    <li class="breadcrumb-item"><a href="{% url 'board_topics' board.pk %}">{{ board.name }}</a></li>
    <li class="breadcrumb-item active">New topic</li>
{% endblock %}

{% block content %}
    <form method="post">
        {% csrf_token %}
        {{ form.as_p }}
        <button type="submit" class="btn btn-success">Post</button>
    </form>
{% endblock %}

Answer 1

if form.is_valid(): GET請求上失敗，因為您僅在request.method == 'POST'時定義form 。

可以通過更改一些縮進來解決此問題：

if request.method == 'POST':
    form = NewTopicForm(request.POST)
    if form.is_valid():
        topic = form.save()
        return redirect('board_topics', pk=board.pk)
else:
    form = NewTopicForm()
return render(request, 'new_topic.html', {'form': form})

Answer 2

我沒有發現縮進的任何問題，但初始化。 請在渲染之前進行初始化！ 進行如下所示的更改肯定可以解決問題，這是擺脫更改的一種非常真實，正確的方法：

def new_topic(request, pk):
    board = get_object_or_404(Board, pk=pk)
    user = User.objects.first()  # TODO: get the currently logged in user
    form = NewTopicForm()
    if request.method == 'POST':
        form = NewTopicForm(request.POST)
        if form.is_valid():
           topic = form.save()
           return redirect('board_topics', pk=board.pk)
        else:
            form = NewTopicForm()
    return render(request, 'new_topic.html', {'form': form})