I am a newbie to Django, GAE, and met some problems when I am trying to build some dynamic forms using Django. The idea is that the selection made from one drop-down box determines value in another field.
In detail, if an user
choose "A" in "Species", then the value in the "body_weight" will be 178. Similarly,
if he choose "B" in "Species", the value in "body_weight" is 1580, and
if choose "C" in "Species", the he can fill in the "body_weight"
I read some examples, and found some features like "init, and super should be included". Thus I modified my codes, but it still did not work.
My problems are:
What is the right position to place "init" and "super"?
Do I need "self.field" here?
All suggestions are welcomed!
Thanks!
Here is the code.
Species_CHOICES=(('178','A'),('1580','B'),('','C'))
class Inp(forms.Form):
Species = forms.ChoiceField(label='Species', choices=Species_CHOICES, initial='A')
#Here detect the choice made by the user
def get_STB_choices(Species):
if Species=='178':
r= 178
elif Species=='1580':
r= 1580
else:
r= 4440
return a
#assign values to a new parameter based on user's choice
def __init__(self, *args, **kwargs):
super(Inp, self).__init__(*args, **kwargs)
body_weight=forms.FloatField(required=True, label='Body weight', initial=get_STB_choices(Species))
#write out in HTML
class InputPage(webapp.RequestHandler):
def get(self):
html = str(Inp())
self.response.out.write(html)
You're going to need Javascript running on the page to update the available selections.
I implemented it one way here. Each time you make a selection, the page makes an AJAX request to get the new form fields that were dependent on the initial change.
https://github.com/dragonx/django-hier-ajax-form
After I did mine, I realized there was already an existing project that did the same thing, but our implementations are pretty different:
https://github.com/digi604/django-smart-selects
btw, I believe usually when you call super() you use it with the name of the current class, so I would have expected
super(Inp, self).__init__(*args, **kwargs)
Related
We are building a wizard using Django 1.4's new form wizard functionality.
The docs on this are very terse and we can't find any advanced examples. We are using a named step wizard (needed to support a listview/datagrid we use) and a session backend.
The wizard is meant to edit roles and linked rights and is built to provide both add and edit functionality. We do this by asking the user in the first step if he/she wants to add or edit.
The next step depends on that choice;
If the user wants to edit, there is a search screen, followed by a listview/datagrid that displays results. The user can then select one of the results and goes to a details-screen, followed by a FilteredSelectMultiple page, allowing him/her to link rights to this role.
If the user wants to add a new role, the search and results screens are skipped and the user goes directly to the details screen, followed by the link-screen.
It all works pretty well, using a condition_dict in urls.py, but we are wondering a couple of things about the general functionality:
When a specific pre-existing role is selected, how can we fill the details and the link-screen with the corresponding data?
Do we instantiate a roles-object and pass it somehow to the two forms, if so, where do we instantiate it and do we need to do that for every form separately (which seems a bit over the top)?
When saving, is it common practice to create another instance of a role object, add the form data to it and save, or can we re-use the object used in the forms somehow?
We have tried overloading get_form_instance to return instances of roles, and we have looked at instance_dict in the docs, but it feels like the wrong approach and there are no examples to be found online, and we're not even sure these are used to pre-fill data or even if we're on the right track.
Logically, I would say in the step that selects an existing role, I need to fill the wizard-variables using an instance of the chosen object, and these get displayed in the forms. At the end of the wizard we reverse the process and get all data from the wizard-variables and add them to a newly instantiated roles-object and save it. Ideally this instance will determine itself if it needs to perform an INSERT or an UPDATE, depending on whether or not the promary key is filled.
If anyone can provide an example, or a nudge in the right direction, it would be very much appreciated.
The code of the wizardview class in views.py is below:
class RolesWizard(NamedUrlSessionWizardView):
def get_template_names(self):
# get template for each step...
if self.steps.current == 'choice':
return 'clubassistant/wizard_neworeditrole.html'
if self.steps.current == 'search':
return 'clubassistant/wizard_searchrole.html'
if self.steps.current == 'results':
return 'clubassistant/wizard_pickrole.html'
if self.steps.current == 'details':
return 'clubassistant/wizard_detailsrole.html'
elif self.steps.current == 'rights':
return 'clubassistant/wizard_roles.html'
def get_context_data(self, form, **kwargs):
# get context data to be passed to the respective templates
context = super(RolesWizard, self).get_context_data(form=form, **kwargs)
# add the listview in the results screen
if self.steps.current == 'results':
# get search text from previous step
cleaned_data = self.get_cleaned_data_for_step('search')
table = RolesTable(Roles.objects.filter(
role_name__contains=cleaned_data['searchrole'])
)
RequestConfig(self.request, paginate={
"per_page": 4,
}).configure(table)
# add the listview with results
context.update({'table': table})
# add a role instance based on the chosen primary key
if self.steps.current == 'rights':
cleaned_data = self.get_cleaned_data_for_step('results')
role_id = cleaned_data['role_uuid']
role = get_object_or_404(Roles, pk=role_id)
context.update({'role': role})
return context
def done(self, form_list, **kwargs):
# this code is executed when the wizard needs to be completed
# combine all forms into a single dictionary
wizard = self.get_all_cleaned_data()
if wizard.get("neworeditrole")=="add":
role = Roles()
else:
role = get_object_or_404(Roles, pk=wizard.get("role_uuid"))
# many-to-many rights/roles
role.role_rights_new_style.clear()
for each_right in wizard.get('role_rights_new_style'):
RightsRoles.objects.create(role=role, right=each_right,)
# other properties
for field, value in self.get_cleaned_data_for_step('details'):
setattr(role, field, value)
role.save()
# return to first page of wizard...
return HttpResponseRedirect('/login/maintenance/roles/wizard/choice/')
For future googlers:
I had some success with using get_form() because it is called before a form is rendered. Start with a couple of ModelForms:
class Wizard1(models.ModelForm):
class Meta:
model = MyModel
fields = ('field0', 'model0')
class Wizard2(models.ModelForm):
class Meta:
model = MyModel
excludes = ('field0', 'model0')
Then, in your SessionWizardView:
class MyWizard(SessionWizardView):
def get_form(self, step=None, data=None, files=None):
form = super(ExtensionCreationWizard, self).get_form(step, data, files)
if step is not None and data is not None:
# get_form is called for validation by get_cleaned_data_for_step()
return form
if step == "0":
# you can set initial values or tweak fields here
elif step == "1":
data = self.get_cleaned_data_for_step('0')
if data is not None:
form.fields['field1'].initial = data.get('field0')
form.fields['field2'].widget.attrs['readonly'] = True
form.fields['field3'].widget.attrs['disabled'] = True
form.fields['model1'].queryset = Model1.objects.filter(name="foo")
return form
The action is all in step 1. You request validated data from step 0 (which triggers another call to get_form() for step 0, so be careful) and then you can access any values that were set in step 0.
I threw in a couple of examples of settings you can change on the fields. You can update a queryset to limit the values in a ChoiceField, or re-display a value again but make it read-only. One caveat I noticed... readonly does not work on ChoiceField. You can make it disabled, but then the value is not propagated when you submit the form.
Let's see if I can help. I did a form wizard that adds steps depending on the answers. At each step I save all forms in a session variable, like so:
def process_step(self, request, form, step):
request.session['form_list'] = self.form_list
request.session['initial'] = self.initial
Then, each time that view is rendered, I instantiate a new form wizard with all the previous data:
def dynamic_wizard(request):
if not request.session.get('form_list'):
form = Wizard([Form1])
else:
form = Wizard(request.session.get('form_list'), initial = request.session['initial'])
return form(context=RequestContext(request), request=request)
I am trying to follow the code listed on https://github.com/alex/django-ajax-validation/blob/master/ajax_validation/views.py
I have been able to understand a small chunk of it. I have added comments stating my understanding of what is happening.
I would really appreciate some assistance on questions I listed in comments next to the lines I couldn't quite follow.
def validate(request, *args, **kwargs):
# I thing it is some sort of initializations but I cannot really understand what's happening
form_class = kwargs.pop('form_class')
defaults = {
'data': request.POST
}
extra_args_func = kwargs.pop('callback', lambda request, *args, **kwargs: {})
kwargs = extra_args_func(request, *args, **kwargs)
defaults.update(kwargs)
form = form_class(**defaults)
if form.is_valid(): #straightforward, if there is no error then the form is valid
data = {
'valid': True,
}
else:
# if we're dealing with a FormSet then walk over .forms to populate errors and formfields
if isinstance(form, BaseFormSet): #I cannot really understand what is BaseFromSet
errors = {}
formfields = {}
for f in form.forms: # I am guessing that this is for when there are multiple form submitted for validation
for field in f.fields.keys(): # I think he is looping over all fields and checking for error. what does add_prefix () return? and what is formfields[]?
formfields[f.add_prefix(field)] = f[field]
for field, error in f.errors.iteritems():
errors[f.add_prefix(field)] = error
if form.non_form_errors():
errors['__all__'] = form.non_form_errors() # what is the '__all__'?
else:
errors = form.errors
formfields = dict([(fieldname, form[fieldname]) for fieldname in form.fields.keys()])
# if fields have been specified then restrict the error list
if request.POST.getlist('fields'): # I am having a hard time understanding what this if statement does.
fields = request.POST.getlist('fields') + ['__all__']
errors = dict([(key, val) for key, val in errors.iteritems() if key in fields])
final_errors = {} # here the author of this code totally lost me.
for key, val in errors.iteritems():
if '__all__' in key:
final_errors[key] = val
elif not isinstance(formfields[key].field, forms.FileField):
html_id = formfields[key].field.widget.attrs.get('id') or formfields[key].auto_id
html_id = formfields[key].field.widget.id_for_label(html_id)
final_errors[html_id] = val
data = {
'valid': False or not final_errors,
'errors': final_errors,
}
json_serializer = LazyEncoder() # Why does the result have to be returned in json?
return HttpResponse(json_serializer.encode(data), mimetype='application/json')
validate = require_POST(validate) # a decorator that requires a post to submit
LazyEncoder
class LazyEncoder(JSONEncoder):
def default(self, obj):
if isinstance(obj, Promise):
return force_unicode(obj)
return obj
form_class = kwargs.pop('form_class')
This is simply pulling the keyword argument, form_class, that was passed in via the URL conf.
(r'^SOME/URL/$', 'ajax_validation.views.validate',
{'form_class': ContactForm}, # this keyword argument.
'contact_form_validate')
BaseFormSet is simply the formset class doing the work behind the scenes. When you don't know, search the source! grep -ri "baseformset" . It's an invaluable tool.
Take a look at at django.forms.formsets to see how formset_factory produces new "formset" classes based on the BaseFormSet, hence the factory part!
I am guessing that this is for when there are multiple form submitted for validation
Yes, that's exactly what a formset is for (dealing with multiple forms)
I think he is looping over all fields and checking for error. what does add_prefix () return? and what is formfields[]?
Yes, that would be looping through the field names.
add_prefix() is for prefixing form field names with a specific form. Because a formset repeats form elements multiple times, each field needs a unique prefix, such as 0-field1, 1-field1, etc.
formfields is just an empty dictionary defined a few lines above.
what is the 'all'?
__all__ is defined at the top of django.forms.forms
NON_FIELD_ERRORS = '__all__'
It's just what non field specific errors (such as constraints across 2 fields) are stored under in the errors dictionary as opposed to errors[fieldname].
I am having a hard time understanding what this if statement does.
The author has left a note:
# if fields have been specified then restrict the error list
if request.POST.getlist('fields'):
It's checking if you specified any specific fields to validate in your URLConf, this is not django but ajax_validation.
You can see that he's overwriting his errors dictionary based on only the fields specified, thus passing on the validation only for those fields.
errors = dict([(key, val) for key, val in errors.iteritems() if key in fields])
here the author of this code totally lost me.
The author has mapped a custom errors and fields dictionary to specific field names with prefixes, (as opposed to the usual FormSet with each form having its own errors dictionary, unaware of the formset itself) which he presumably uses in the AJAX response to validate all fields.
Normally, you can iterate over a formset and go through the errors on a form by form basis, but not so if you need to validate all of them through ajax.
The line pulling html_id should be straight forward most of the time, but it's there because form widgets CAN add interesting things to the end of the ID's based on whether or not the widget is a radio select for example.
From source comments :
# RadioSelect is represented by multiple <input type="radio"> fields,
# each of which has a distinct ID. The IDs are made distinct by a "_X"
# suffix, where X is the zero-based index of the radio field. Thus,
# the label for a RadioSelect should reference the first one ('_0').
Why does the result have to be returned in json?
Because it's an ajax request and javascript easily eats json.
2- could you go through these lines of code...
extra_args_func = kwargs.pop('callback', lambda request, *args, **kwargs: {})
Either return a keyword argument named 'callback' (which if passed in, is supposed to be a function that accepts request and return a dictionary), and if it wasn't, return a lambda function that only returns an empty dictionary.
I'm not sure what the specific use is for the extra context. You could use it to run arbitrary snippets of code without modifying or subclassing ajax_validation...
It might help you to run this code, and put a debugger breakpoint in somewhere so you can step through and examine the variables and methods. You can do this by simply putting this line where you want to break:
import pdb; pdb.set_trace()
and you will be dumped into the debugger in the console.
I am trying to implement a MultiValueField for IP Adress/Domain Name entries. It works as expected for entering data.
My Problem is that if I want to display the form bound to specific data, the IP Address/Domain Name field stays empty. All other fields are filled with the desired data. If I use a normal CharField, I get the data that I would expect. But it does not work with my custom field.
I have tracked it down to the fact that my custom MultiWidget does not call its decompress method.
Here is my Field:
class accessIPField(forms.MultiValueField):
"""
custom Field for access IP
"""
def __init__(self, *args, **kwargs):
self.fields=(
forms.IPAddressField(label='IP Adress'),
forms.CharField(max_length=50,label='Domain Name')
)
self.widget=accessIPWidget()
super(accessIPField,self).__init__(self.fields,self.widget, *args, **kwargs)
def compress(self,data_list):
if data_list:
return " ".join(data_list)
And here is my widget:
class accessIPWidget(forms.MultiWidget):
"""
Widget to display IP Adress / Domain name pairs
"""
def __init__(self,*args,**kwargs):
self.widgets=(forms.TextInput(),forms.TextInput())
super(accessIPWidget,self).__init__(self.widgets,*args,**kwargs)
def decompress(self,value):
print 'decompress called'
if value:
return value.rsplit()
return [None,None]
def format_output(self, rendered_widgets):
return u'\n'.join(rendered_widgets)
The whole thing is called (in a larger context) as
self.fields['access_IPs'] = accessIPField()
Now as you can see, I put a print statement in my compress method, and I never get to see that statement. Also, if I rename compress to something like foobar, I would expect (according to the django code for MultiWidget) to get the NotImplementedError, which is not the case. Any suggestions?
I am using python 2.6.5, django 1.1 on ubuntu server 10.04.
It turns out that the problem was with the value_from_datadict() method as implemented by MultiWidget. First of all, it allready returned a list, so that is why decompress() was not called in the first place. Secondly, it allways returen a [None,None] list, so that is why the bound form stayed empty.
I needed to implement my own (within my accessIPWidget class):
def value_from_datadict(self, data, files, name):
try:
return data.get(name,None).rsplit()
except AttributeError:
return [widget.value_from_datadict(data, files, name + '_%s' % i) for i, widget in enumerate(self.widgets)]
Now the last line is what the original method did. In order to get the data into the bound form, I needed to add data.get(name,None).rsplit().
As far as I understand, the original value_from_datadict method only works for unbound fields. Because it changes the name of the original field to name + '_%s', which is what you get when pressing the submit button. In order to fill in a bound method, the datadict needs to be queried for 'name' only.
Hm, not shure if there is a way around this, but it seems to me that this behaviour should at least be documented somewhere.
Maybe I misunderstood something?
I am writing an application in Django, which uses [year]/[month]/[title-text] in the url to identitfy news items. To manage the items I have defined a number of urls, each starting with the above prefix.
urlpatterns = patterns('msite.views',
(r'^(?P<year>[\d]{4})/(?P<month>[\d]{1,2})/(?P<slug>[\w]+)/edit/$', 'edit'),
(r'^(?P<year>[\d]{4})/(?P<month>[\d]{1,2})/(?P<slug>[\w]+)/$', 'show'),
(r'^(?P<year>[\d]{4})/(?P<month>[\d]{1,2})/(?P<slug>[\w]+)/save$', 'save'),
)
I was wondering, if there is a mechanism in Django, which allows me to preprocess a given request to the views edit, show and save. It could parse the parameters e.g. year=2010, month=11, slug='this-is-a-title' and extract a model object out of them.
The benefit would be, that I could define my views as
def show(news_item):
'''does some stuff with the news item, doesn't have to care
about how to extract the item from request data'''
...
instead of
def show(year, month, slug):
'''extract the model instance manually inside this method'''
...
What is the Django way of solving this?
Or in a more generic way, is there some mechanism to implement request filters / preprocessors such as in JavaEE and Ruby on Rails?
You need date based generic views and create/update/delete generic views maybe?
One way of doing this is to write a custom decorator. I tested this in one of my projects and it worked.
First, a custom decorator. This one will have to accept other arguments beside the function, so we declare another decorator to make it so.
decorator_with_arguments = lambda decorator: lambda * args, **kwargs: lambda func: decorator(func, *args, **kwargs)
Now the actual decorator:
#decorator_with_arguments
def parse_args_and_create_instance(function, klass, attr_names):
def _function(request, *args, **kwargs):
model_attributes_and_values = dict()
for name in attr_names:
value = kwargs.get(name, None)
if value: model_attributes_and_values[name] = value
model_instance = klass.objects.get(**model_attributes_and_values)
return function(model_instance)
return _function
This decorator expects two additional arguments besides the function it is decorating. These are respectively the model class for which the instance is to be prepared and injected and the names of the attributes to be used to prepare the instance. In this case the decorator uses the attributes to get the instance from the database.
And now, a "generic" view making use of a show function.
def show(model_instance):
return HttpResponse(model_instance.some_attribute)
show_order = parse_args_and_create_instance(Order, ['order_id'])(show)
And another:
show_customer = parse_args_and_create_instance(Customer, ['id'])(show)
In order for this to work the URL configuration parameters must contain the same key words as the attributes. Of course you can customize this by tweaking the decorator.
# urls.py
...
url(r'^order/(?P<order_id>\d+)/$', 'show_order', {}, name = 'show_order'),
url(r'^customer/(?P<id>\d+)/$', 'show_customer', {}, name = 'show_customer'),
...
Update
As #rebus correctly pointed out you also need to investigate Django's generic views.
Django is python after all, so you can easily do this:
def get_item(*args, **kwargs):
year = kwargs['year']
month = kwargs['month']
slug = kwargs['slug']
# return item based on year, month, slug...
def show(request, *args, **kwargs):
item = get_item(request, *args, **kwargs)
# rest of your logic using item
# return HttpResponse...
Here is the field declaration in a form:
max_number = forms.ChoiceField(widget = forms.Select(),
choices = ([('1','1'), ('2','2'),('3','3'), ]), initial='3', required = True,)
I would like to set the initial value to be 3 and this doesn't seem to work. I have played about with the param, quotes/no quotes, etc... but no change.
Could anyone give me a definitive answer if it is possible? And/or the necessary tweak in my code snippet?
I am using Django 1.0
Try setting the initial value when you instantiate the form:
form = MyForm(initial={'max_number': '3'})
This doesn't touch on the immediate question at hand, but this Q/A comes up for searches related to trying to assign the selected value to a ChoiceField.
If you have already called super().__init__ in your Form class, you should update the form.initial dictionary, not the field.initial property. If you study form.initial (e.g. print self.initial after the call to super().__init__), it will contain values for all the fields. Having a value of None in that dict will override the field.initial value.
e.g.
class MyForm(forms.Form):
def __init__(self, *args, **kwargs):
super(MyForm, self).__init__(*args, **kwargs)
# assign a (computed, I assume) default value to the choice field
self.initial['choices_field_name'] = 'default value'
# you should NOT do this:
self.fields['choices_field_name'].initial = 'default value'
You can also do the following. in your form class def:
max_number = forms.ChoiceField(widget = forms.Select(),
choices = ([('1','1'), ('2','2'),('3','3'), ]), initial='3', required = True,)
then when calling the form in your view you can dynamically set both initial choices and choice list.
yourFormInstance = YourFormClass()
yourFormInstance.fields['max_number'].choices = [(1,1),(2,2),(3,3)]
yourFormInstance.fields['max_number'].initial = [1]
Note: the initial values has to be a list and the choices has to be 2-tuples, in my example above i have a list of 2-tuples. Hope this helps.
I ran into this problem as well, and figured out that the problem is in the browser. When you refresh the browser is re-populating the form with the same values as before, ignoring the checked field. If you view source, you'll see the checked value is correct. Or put your cursor in your browser's URL field and hit enter. That will re-load the form from scratch.
Both Tom and Burton's answers work for me eventually, but I had a little trouble figuring out how to apply them to a ModelChoiceField.
The only trick to it is that the choices are stored as tuples of (<model's ID>, <model's unicode repr>), so if you want to set the initial model selection, you pass the model's ID as the initial value, not the object itself or it's name or anything else. Then it's as simple as:
form = EmployeeForm(initial={'manager': manager_employee_id})
Alternatively the initial argument can be ignored in place of an extra line with:
form.fields['manager'].initial = manager_employee_id
Dave - any luck finding a solution to the browser problem? Is there a way to force a refresh?
As for the original problem, try the following when initializing the form:
def __init__(self, *args, **kwargs):
super(MyForm, self).__init__(*args, **kwargs)
self.base_fields['MyChoiceField'].initial = initial_value
To be sure I need to see how you're rendering the form. The initial value is only used in a unbound form, if it's bound and a value for that field is not included nothing will be selected.