dutils.utils.form_handler is a generic view that can be used for handling forms.
Some ajax heavy apps require a lot of views that are merely a wrapper around the form. This generic view can be used for them.
| Parameters: |
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|---|---|
| Return type: | instance of HttpResponse subclass |
form_handler can be used in various scenarios.
A typical form handler in django is the following view:
from myproj.myapp.forms import MyApp
def my_form_view(request):
if request.method == "POST":
form = MyForm(request.POST)
if form.is_valid():
form.save()
return HttpResponseRedirect("/somewhere/")
else:
form = MyForm()
return render_to_response(
"my_form.html", { "form": form },
context_instance=RequestContext(request)
)
This can be handled by form_handler by putting the following entries in urls.py:
from django.conf.urls.defaults import *
urlpatterns = patterns('',
url(r'^my-form/$',
"dutils.utils.form_handler",
{
'template': 'my_form.html',
"form_cls": "myproj.myapp.forms.MyForm",
"next": "/somewhere/",
},
),
)
Sometimes when lets say you created a new object, and user should be redirected to that object, instead of a static url, next parameter is not suffecient. In such cases, do not pass next and let form.save() return the URL. form_handler will redirect user to this url.:
class CreateBookForm(forms.Form):
title = forms.CharField(max_length=50)
def save(self):
book = Book.objects.create(title=title)
return book.get_absolute_url()
urlpatterns = patterns('',
url(r'^create-book/$',
"dutils.utils.form_handler",
{
'template': 'create-book.html',
"form_cls": CreateBookForm,
"pass_request": False,
},
),
)
Sometimes for valid form processing, some aspect of request has to be know. In this case make sure your Form can take request as the first parameter, and set pass_request to True.:
class CreateBookForm(forms.Form):
title = forms.CharField(max_length=50)
def __init__(self, request, *args, **kw):
super(CreateBookForm, self).__init__(*args, **kw)
self.request = request
def save(self):
book = Book.objects.create(title=title, user=self.request.user)
return book.get_absolute_url()
urlpatterns = patterns('',
url(r'^create-book/$',
"dutils.utils.form_handler",
{
'template': 'create-book.html',
"form_cls": CreateBookForm,
"pass_request": True,
"require_login": True,
},
),
)
dutils.utils comes with a utility class derived from Form known as RequestForm. This form takes care of storing the request passed in constructor, so the above form can be re written as:
class CreateBookForm(dutils.utils.RequestForm):
title = forms.CharField(max_length=50)
def save(self):
book = Book.objects.create(title=title, user=self.request.user)
return book.get_absolute_url()
urlpatterns = patterns('',
url(r'^create-book/$',
"dutils.utils.form_handler",
{
'template': 'create-book.html',
"form_cls": CreateBookForm,
"require_login": True,
},
),
)
Note
since pass_request is True by default this can be omitted.
Sometimes being logged in is not enough, you may want users to satisfy some kind of condition before they can access the form, for example they account if valid, or it has enough balance or whatever.
This can be achieved by a combination of require_login and login_url. Lets say our user object has can_create_books() method on its UserProfile.
Also lets assume that “/make-payment/” is the URL user will go to if they do not have permission to create books.
Here is how to handle this situation:
def can_create_books(request):
if not request.user.is_authenticated(): return False
return request.user.get_profile().can_create_books()
urlpatterns = patterns('',
url(r'^create-book/$',
"dutils.utils.form_handler",
{
'template': 'create-book.html',
"form_cls": CreateBookForm,
"require_login": can_create_books,
"login_url": "/make-payment/",
},
),
)
Note
require_login can be a callable. If its a callable, it will be passed request as the first parameter.
Note
require_login can return the string “404”, in which case instead of redirecting user to a separate page, they will be presented with 404 error. This may be the suitable behaviour if a user would never be allowed access to a page, like edit page for an object not owned by that user.
Django websites usually have clean URLs, which means no “/edit-book/?id=123”, rather “/book/123/edit/”. We have to handle cases where data is coming from URLs, instead of request parameters, to initialize the form.
For this use case form_handler requires forms with .init() method.
Consider the original view:
@login_required
def edit_book(request, book_id):
book = get_object_or_404(Book, id=book_id)
if not book.user == request.user:
Http404
if request.method == "POST":
form = BookEditForm(book, request.POST)
if form.is_valid():
form.save()
return book.get_absolute_url()
else:
form = BookEditForm(book)
return render_to_response(
"edit-book.html", {"form": form, "book": book},
context_instance=RequestContext(request)
)
With urls.py containing:
from django.conf.urls.defaults import *
urlpatterns = patterns('',
# other urls
url(r'^book/(?P<book_id>[\d]+)/edit/$', "myproj.myapp.view.edit_book")
)
And forms.py with something like:
from django import forms
class BookEditForm(forms.Form):
title = forms.CharField(max_length=50)
def __init__(self, book, *args, **kw):
super(BookEditForm, self).__init__(*args, **kw)
self.book = book
self.fields["title"].initial = book.title
def save(self):
self.book.title = self.cleaned_data["title"]
self.book.save()
To handle this define .init() on BookEditForm, and put the view logic for loading the book and doing validation in it:
from django import forms
class BookEditForm(utils.RequestForm):
title = forms.CharField(max_length=50)
def init(self, book_id):
self.book = get_object_or_404(Book, id=book_id)
if not self.book.user == self.request.user:
Http404
self.fields["title"].initial = self.book.title
def save(self):
self.book.title = self.cleaned_data["title"]
self.book.save()
We do not need the view now, and use the form_handler like so:
urlpatterns = patterns('',
fhurl(
r'^book/(?P<book_id>[\d]+)/edit/$',
"myproj.myapp.forms.BookEditForm", template="edit-book.html",
require_login=True
)
)
form_handler will detect that the form has .init(), so it will call it. The extra argument passed from the url, book_id, will be passed to .init() as keyword argument.
Note
Note that if .init() returns something, it is returned directly to users, which means, init() can perform all kinds of checks, and redirect users to different portions of site if required.
Lets say we want to export all this as ajax. You actually don’t have to do anything, just pass “json=true” as a REQUEST parameter. You don’t even have to do that if request is coming from a browser with proper headers, as required by is_ajax.
The form will return JSON objects, with parameter success which is true or false.
$ curl -d "username=newf&field=username&json=true" "http://localhost:8000/register/"
{"errors": {"password1": ["This field is required."], "email": ["This field is required."]}, "success": false}
If its true when everything goes well, in this case, it will contain response parameter, which will be JSON encoded value of whatever was returned by the form.save().
success is false if there was some form validation error, or if redirect is required. If redirect is required when conditions are not met, JSON contains a parameter redirect which contains the URL to which user has to be redirected.
If success is false because of form validation errors, a property errors contains JSON encoded error messages.
Note
In ajax mode, if a GET request is made, a JSON representation of form is returned, containing initial values, lables, help_text etc. This can be used to auto generate form, or to get initial values etc.
Sometimes implicit conversion of object returned by form.save() can be limiting in scenarios where same form is being used both for ajax handling and as normal webform.
Eg, /create-book/ when accessed via browser would want to return user to the newly created book’s permalink on success, while when the same URL is invoked through ajax, we want to return the JSON representation of the book.
To handle this, give your form a .get_json() method, which when available is called, and its output is returned to user for ajax invocation, and .save() can safely return the permalink of the book, which will lead to browser getting redirected to that user.
Eg:
class CreateBook(utils.RequestForm):
# fields
# validation
def get_json(self, saved):
return self.book.__dict__ # gets JSONified for JSON calls
def save(self):
self.book = create_book(self.cleaned_data)
return self.book.get_absolute_url() # browser gets redirected here
dutils comes with a utility function fhurl, that can be used django.conf.urls.defaults.url.
Original urlconf:
urlpatterns = patterns('',
url(r'^create-book/$',
"dutils.utils.form_handler",
{
'template': 'create-book.html',
"form_cls": CreateBookForm,
},
),
)
With fhurl:
urlpatterns = patterns('',
fhurl(r'^create-book/$', CreateBookForm, template='create-book.html')
)
form_handler can be used for validating partially filled forms for as you type validation of web forms.
This feature can be setup either on the URL basis by passing validate_only to form_handler in urls.py, or on a per request basis by passing validate_only request parameter.
If its being done on request basis, no setup is required, just pass the validate_only parameter:
$ curl -d "validate_only=true&username=&field=username" "http://localhost:8000/register/"
{"errors": "This field is required.", "valid": false}
$ curl -d "validate_only=true&username=amitu&field=username" "http://localhost:8000/register/"
{"errors": "This username is already taken. Please choose another.", "valid": false}
$ curl -d "validate_only=true&username=newf&field=username" "http://localhost:8000/register/"
{"errors": "", "valid": true}
Some javascript to handle it:
$(function(){
$("#id_username, #id_password, #id_password2, #id_email").blur(function(){
var url = "/register/?validate_only=true&field=" + this.name;
var field = this.name;
$.ajax({
url: url, data: $("#registration_form").serialize(),
type: "post", dataType: "json",
success: function (response){
if(response.valid)
{
$("#"+field+"_errors").html("Sounds good");
}
else
{
$("#"+field+"_errors").html(response.errors);
}
}
});
});
});