python - 实用 Django 项目 - 第 183 和 184 页

Question

第 183 和 184 页有以下代码:

def edit_snippet(request, snippet_id):
    snippet = get_object_or_404(Snippet, pk=snippet_id)
    if request.user.id != snippet.author.id:
        return HttpResponseForbidden()
    if request.method == 'POST':
        form = SnippetForm(instance=snippet, data=request.POST)
        if form.is_valid():
            snippet = form.save()
            return HttpResponseRedirect(snippet.get_absolute_url())
    else:
        form = SnippetForm(instance=snippet)
    return render_to_response('cab/snippet_form.html',{ 'form': form, 'add': False })
edit_snippet = login_required(edit_snippet)

为什么需要在这里添加数据属性:

form = SnippetForm(instance=snippet, data=request.POST)

实例属性还不够吗？

如果请求方法不是 POST，那么它可以是任何方法，但通常是 GET 方法。为什么在这种情况下没有数据属性？为什么需要考虑其他请求方法？我们不能直接写:

def edit_snippet(request, snippet_id):
    snippet = get_object_or_404(Snippet, pk=snippet_id)
    if request.user.id != snippet.author.id:
        return HttpResponseForbidden()
    if request.method == 'POST':
        form = SnippetForm(instance=snippet, data=request.POST)
        if form.is_valid():
            snippet = form.save()
            return HttpResponseRedirect(snippet.get_absolute_url())
    return render_to_response('cab/snippet_form.html',{ 'form': form, 'add': False })
edit_snippet = login_required(edit_snippet)

如果请求方法不是 POST，那么不让用户编辑他的代码片段对我来说听起来更合乎逻辑。你能解释一下这些要点吗？

Answer 1

这是 Django 的做法:相同的 View 用于显示要编辑的表单 (GET)，然后验证它 (POST)。

请参阅 docs 中的此示例:

The standard pattern for processing a form in a view looks like this:

def contact(request):
    if request.method == 'POST': # If the form has been submitted...
        form = ContactForm(request.POST) # A form bound to the POST data
        if form.is_valid(): # All validation rules pass
            # Process the data in form.cleaned_data
            # ...
            return HttpResponseRedirect('/thanks/') # Redirect after POST
    else:
        form = ContactForm() # An unbound form

    return render_to_response('contact.html', {
        'form': form,
    })