Django Generic Form Handler View – fhurl¶

fhurl.form_handler is a generic view that can be used for handling forms.

Install fhurl using:

$ easy_install fhurl

fhurl is being developed on http://github.com/amitu/fhurl/.

See the Changelog: https://github.com/amitu/fhurl/blob/master/ChangeLog.rst.

form_handler¶ fhurl. form_handler ( request, form_cls, require_login=False, block_get=False, next=None, template=None, login_url=None, pass_request=True, ajax=False, validate_only=False ) ¶ 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: request – request object, instance of HttpRequest

– request object, instance of HttpRequest form_cls (string or instance of Form subclass.) – form class to use

(string or instance of Form subclass.) – form class to use require_login – boolean or callable, if this is true, use must login before they can interact with the form

– boolean or callable, if this is true, use must login before they can interact with the form block_get – if true, GET requests are not allowed.

– if true, GET requests are not allowed. next – if passed, user will be redirected to this url after success

– if passed, user will be redirected to this url after success template – if passed, this template will be used to render form

– if passed, this template will be used to render form login_url – user will be redirected to this user if login is required

– user will be redirected to this user if login is required pass_request – form instance would be created with request as first parameter if this is true

– form instance would be created with request as first parameter if this is true ajax – if this is true, form_handler will only return JSON data

– if this is true, form_handler will only return JSON data validate_only – if this is true, form_handler will only validate fields and wont call form.save() Return type: instance of HttpResponse subclass

fhurl¶ fhurl. fhurl ( reg, form_cls, decorator=labmda x: x, **kw ) ¶ This is a utility function to be used in urls.py for convenience. Parameters: reg – regular expression as used in django urls.

– regular expression as used in django urls. form_cls (string or django.forms.Form subclass.) – The form class to use.

(string or django.forms.Form subclass.) – The form class to use. decorator – the decorator to use, optional.

– the decorator to use, optional. kw – rest of the keyword arguments as described above. form_handler and fhurl can be used in various scenarios.

Simple Form Handling¶ A typical form handler in django is the following view: from myproj.myapp.forms import MyForm 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 fhurl by putting the following entries in urls.py: from django.conf.urls.defaults import * from fhurl import fhurl urlpatterns = patterns ( '' , fhurl ( r'^my-form/$' , "myproj.myapp.forms.MyForm" , template = 'my_form.html' , next = "/somewhere/" , pass_request = False ), )

The URL To Be Redirected Is Variable¶ 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 ( '' , fhurl ( r'^create-book/$' , CreateBookForm , template = 'create-book.html' , pass_request = False , ), )

Access To Request Parameters Required¶ Sometimes for valid form processing, some aspect of request has to be know. In this case make sure your Form constructore 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 ( '' , fhurl ( r'^create-book/$' , CreateBookForm , template = 'create-book.html' , require_login = True , ), ) fhurl comes with a utility class derived from Form known as RequestForm . This form takes care of storing the request passed in constructor, so the above form can be re written as: class CreateBookForm ( fhurl . RequestForm ): title = forms . CharField ( max_length = 50 ) def save ( self ): book = Book . objects . create ( title = title , user = self . request . user ) return book . get_absolute_url () urlpatterns = patterns ( '' , fhurl ( r'^create-book/$' , CreateBookForm , template = 'create-book.html' ), )

Only Users With Valid Account Can Access The Form¶ 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 their account is 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 ( '' , fhurl ( r'^create-book/$' , CreateBookForm , login_url = "/make-payment/" , template = 'create-book.html' , require_login = can_create_books , ), ) Note require_login can be a callable. If its a callable, it will be passed request as the first parameter. Note In this example, make sure that /make-payment/ redirects user to /login/ if user is not logged in.

Forms That Take Parameters From URL¶ 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/$' , "myproj.myapp.view.edit_book" ) ) And forms.py with something like: from django import forms class BookEditForm ( forms . Form ): title = forms . CharField ( max_length = 50 ) def __init__ ( self , book , * args , ** kw ): super ( BookEditForm , self ) . __init__ ( * args , ** kw ) self . book = book self . fields [ "title" ] . initial = book . title def save ( self ): self . book . title = self . cleaned_data [ "title" ] self . book . save () To handle this define .init() on BookEditForm, and put the view logic for loading the book and doing validation in it: from django import forms class BookEditForm ( fhurl . RequestForm ): title = forms . CharField ( max_length = 50 ) def init ( self , book_id ): self . book = get_object_or_404 ( Book , id = book_id ) if not self . book . user == self . request . user : Http404 self . fields [ "title" ] . initial = self . book . title def save ( self ): self . book . title = self . cleaned_data [ "title" ] self . book . save () We do not need the view now, and use the form_handler like so: urlpatterns = patterns ( '' , fhurl ( r'^book/(?P<book_id>[\d]+)/edit/$' , 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.

Doing Ajax¶ 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. $ 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 } The form will return JSON objects, with parameter success which is true or 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. A jquery plugin for fhurl forms: $ . fn . handle_form = function ( cb ) { return this . unbind ( "submit" ). submit ( function ( e ){ e . preventDefault () var form = this var $form = $ ( this ) $ . post ( form . action , $form . serialize (), function ( d ){ if ( d . success ) { if ( cb ) cb ( d . response ) } else { $ ( ".error" , form ). empty () $ . each ( d . errors , function ( item , key ){ $ ( "#error_" + key ). append ( "<li>" + item + "</li>" ) }) } }, "json" ) }) }

Using Same Form For JSON Access And Normal Web Access¶ 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 ( fhurl . 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