当需要 POST 类型时，请求类型为 GET

Question

我正在尝试构建一个使用表单上传文件的简单 Django 应用程序，但是每当我运行我在本地主机上的应用程序时，我在尝试加载根页面时收到以下错误 - http://127.0.0.1:8000/ :

UnboundLocalError at /

local variable 'form' referenced before assignment

/Users/danieloram/PycharmProjects/FileUploaderProject/FileUploader/views.py in index
                                   {'images': images, 'form': form},
...
▶ Local vars

以下是相关 view.py、models.py 和 index.html（问题中的视图）文件的代码：

views.py##

from django.shortcuts import render
from django.http import HttpResponseRedirect
from django.shortcuts import render_to_response
from django.template import RequestContext

#import models and forms
from FileUploader.models import Image
from FileUploader.forms import ImageUploadForm

# Create your views here.

#this view will respond to file uploads
def index(request):
    print("View loaded")
    if request.method =='POST':
        #create a form from the model I made
        form = ImageUploadForm(request.POST, request.FILES)
        #check form contains no errors
        if form.is_valid():
            #create a new image and save it! file param must be name of attribute in ImageUploadForm
            newImage = Image(imageFile = request.FILES['imageFile'])
            newImage.save()
            #redirect to success page!
            return HttpResponseRedirect('/success/')
        else:
            #create an empty form if it failed
            form = ImageUploadForm()
    else:
        #view will not load as error thrown from nothing being assigned to the form.
        print("Form method was not POST! nothing was assigned to the form and it will fail.")
    images = Image.objects.all()
    #render the page and pass the dictionary to the view
    return render_to_response('index.html',
                              {'images': images, 'form': form},
                              context_instance=RequestContext(request))
def success(request):
    debug = str(request)
    return render(request, 'success.html', {'debug': debug})

models.py##

from django.db import models

# Create your models here.

#simple model for creating image objects
class Image(models.Model):
    imageFile = models.FileField(upload_to='images/%Y/%m/%d')

index.html##

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    {% load staticfiles %}
    <link rel="stylesheet" type="text/css" href="{% static "style.css" %}">
    <title>Daniel Oram's FileUploading Django Project</title>
</head>
<body>
<div class="container">
    <div id="buffer"></div>
    <div id="panel">
        <p>Choose a file to upload</p>
        <form id="form" action="{% url 'index' %}" method="post" enctype="multipart/form-data">
            <input id="input" type="file" value="Enter Image here for upload" width="100">
            <input type="submit" value="Submit" width="50">
            <!-- I need csrf_token because I used RequestContext in the view -->
            {% csrf_token %}
            <p>{{ form.non_field_errors }}</p>
            <p>{{ form.imageFile.label }} {{ form.imageFile.help_text }}</p>
            <p>
                {{ form.imageFile.error_messages }}
                {{ form.imageFile }}
            </p>
        </form>
    </div>
    <!--List the files already uploaded to the webapp. -->
    <div id="list_of_Images">
        {% if images %}
        <ul>
            <!--Iterate Images stored in media directory and display a link for each -->
            {% for image in images %}
            <li><a href='{{ image.imageFile.url }}'>{{ image.imageFile.name }}</a></li>
            {% endfor %}
        </ul>
        {% else %}
        <p>There are no Images that have been previously uploaded :(</p>
        {% endif %}
    </div>
</div>
</body>
</html>

我在调试方面的努力

目前通过调试发现错误是由于views.py的index方法中没有初始化form变量导致的，因为if request.method =='POST':总是评估为 False 因为 request 是 GET 方法..

任何人都可以帮助向我解释如何在 Django 中发出 POST 请求而不是针对此上下文的 GET 请求，从而解决我的错误并加载页面。我什至不在乎表格是否不起作用，我只是想获得解决方案方面的帮助。谢谢！ PS - urls.py 文件设置正确。

解决方案

在这种情况下：

Get 请求在页面初始加载时执行。
Post提交表单数据时请求
需要初始化表单变量，以便在初始页面加载时传递给视图。
用于初始页面加载的 Else 子句初始化表单附加到错误的 if 语句并且无法访问。

正确的索引方法

def index(request):
    print("View loaded")
    if request.method =='POST':
        form = ImageUploadForm(request.POST, request.FILES)
        if form.is_valid():
            newImage = Image(imageFile = request.FILES['imageFile'])
            newImage.save()
            return HttpResponseRedirect('/success/')       
    else:
        form = ImageUploadForm()
    images = Image.objects.all()
    return render_to_response('index.html',
                              {'images': images, 'form': form},
                              context_instance=RequestContext(request))

Answer 1

如果您在浏览器中提交表单，通常的工作流程是：

您使用 GET 请求浏览到 URL
浏览器用POST请求提交数据（因为表单有action="POST"）
如果表单有效，您将被重定向到成功的 URL

因此，与其询问如何将所有请求更改为 POST，不如让您的代码适用于初始 GET 请求。您可以通过在 else 分支中创建一个未绑定的表单来做到这一点。

    if request.method =='POST':
        # create a form bound to the post data
        form = ImageUploadForm(request.POST, request.FILES)
        ...
    else:
        # create an unbound form for the original GET request
        form = ImageUploadForm()
        ...

您可能会发现阅读有关 working with forms 的 Django 文档很有用。示例视图与您尝试执行的操作非常相似。

Answer 2

您的问题不在于请求方法（显然您首先需要执行 GET 以呈现表单，以便您可以 POST 它），但事实上您 don 't 绑定名称 "form" wjen 它是 GET:

def index(request):
    print("View loaded")
    if request.method =='POST':
        form = ImageUploadForm(request.POST, request.FILES)
        if form.is_valid():
            newImage = Image(imageFile = request.FILES['imageFile'])
            newImage.save()
            return HttpResponseRedirect('/success/')    

        # this part is wrong : if the validation failed,
        # you don't want to create a new empty form but
        # redisplay the failed form so you can display
        # the validation errors
        #else:
        #    #create an empty form if it failed
        #    form = ImageUploadForm()

    else:
        ## view will not load as error thrown 
        ## from nothing being assigned to the form.
        # => actually the real error is that you dont 
        #    define the *name* 'form' at all
        #    in this branch...
        #    IOW that's where you want to create 
        #    an "empty" form so the user can fill and
        #    submit it
        form = ImageUploadForm()

当需要 POST 类型时，请求类型为 GET

Request type is GET when POST type is needed

python

django

post

django-forms

django-views