Django - app.views.add didn't return an HttpRe

问题:

This is my view add in the file views.py

def add(request):
#se usaran las categorias para esto,se pasaran en locals()
categorias = Categoria.objects.all()
if request.method == "POST":
    form = EnlaceForm(request.POST)
    if form is valid():
        form.save()
        return HttpResponseRedirect("/")
    else:
        form = EnlaceForm()

    template = "form.html"
    return render_to_response(template, 
                            context_instance = RequestContext(request,locals()))

This is my file urls.py in the which I define the "add" url

from django.conf.urls import patterns, include, url
from django.contrib import admin
admin.autodiscover()

urlpatterns = patterns('',
    # Examples:
    #url(r'^$', 'app.views.hora_actual', name='hora_actual'),
    url(r'^$', 'app.views.home', name='home'),
    url(r'^minus/(\d+)$', 'app.views.minus', name='minus'),
    url(r'^plus/(\d+)$', 'app.views.plus', name='plus'),
    url(r'^categoria/(\d+)$', 'app.views.categoria', name='categoria'),
    url(r'^add/$','app.views.add', name="add"),

# url(r'^proyecto2/', include('proyecto2.foo.urls')),

# Uncomment the admin/doc line below to enable admin documentation:
    url(r'^admin/doc/', include('django.contrib.admindocs.urls')),

# Uncomment the next line to enable the admin:
    url(r'^admin/', include(admin.site.urls)),

)

In the template "form.html" the token {% csrf_token %} and the {{form.as_p}} check that the form was valid

<section id="contenido">
     <form method="post">
    <div id="form">
      {% csrf_token %}
    {{form.as_p}}
    <input type="submit">
 </form>
</div>
</section>

But, when I call the url in the browser 127:0.0.1:8000/add , I get this response or output:

ValueError at /add/

The view app.views.add didn't return an HttpResponse object.
Request Method: GET
Request URL:    http://127.0.0.1:8000/add/
Django Version: 1.5.2
Exception Type: ValueError
Exception Value:    
The view app.views.add didn't return an HttpResponse object.
Exception Location: C:\Python27\lib\site-packages\django\core\handlers\base.py in get_response, line 133
Python Executable:  C:\Python27\python.exe
Python Version: 2.7.5
Python Path:    
['C:\\django-projects\\tests\\proyecto2',
'C:\\Python27\\lib\\site-packages\\setuptools-0.9.6-py2.7.egg',
'C:\\Python27\\python27.zip',
'C:\\Python27\\DLLs',
'C:\\Python27\\lib',
'C:\\Python27\\lib\\plat-win',
'C:\\Python27\\lib\\lib-tk',
'C:\\Python27',
'C:\\Python27\\lib\\site-packages',
'C:\\Python27\\lib\\site-packages\\win32',
'C:\\Python27\\lib\\site-packages\\win32\\lib',
'C:\\Python27\\lib\\site-packages\\Pythonwin',
'C:\\Python27\\lib\\site-packages\\setuptools-0.6c11-py2.7.egg-info']
 Server time:   Thu, 12 Sep 2013 13:16:44 -0500

 Traceback Switch to copy-and-paste view

 C:\Python27\lib\site-packages\django\core\handlers\base.py in get_response
                raise ValueError("The view %s.%s didn't return an HttpResponse object."    % (callback.__module__, view_name)) ...
 ▶ Local vars

I knew that all function based view receive an request object and return an HttpRespose Object, but, what is the difference between HttpResponse and render_to_response object

In that sense, I don't what could be my problem. Thanks for your help.

回答1:

Your render render_to_response is indented one level to the right.

By default, the view is rendered as GET (request.method=='GET'). You had return render_to_response(..) only in the POST section, so when the request processes def add (as a GET request the first time), there is no HttpResponse object returned. Hence the error.

def add(request):
    #se usaran las categorias para esto,se pasaran en locals()
    categorias = Categoria.objects.all()
    if request.method == "POST":
        form = EnlaceForm(request.POST)
        if form is valid():
            form.save()
            return HttpResponseRedirect("/")
    else:
        form = EnlaceForm()

    template = "form.html"
    return render_to_response(template, 
                                context_instance = RequestContext(request,locals()))

Note the indentation of the else: block too.