kwargs with class based views

Using Django Mystery Errors
1

Hello,

I have problems passing kwargs parameters to class based views

urls.py
path('convertST', views.ConvertST.as_view(machine_model =  None, machineST = None), name='convertST'),

views.py:
class ConvertST( FormView):
    template_name = 'app_fabric/machineST_create.html'
    form_class = bmf.CommunitySTGlobalForm
    machine_model = None
    machineST = None

in another view, success url is to redirect to convertST

def get_success_url(self):
 .....
    return revers('app_name:convertST', kwargs = {'machineST' : '1'})

This raises the exception django.urls.exceptions.NoReverseMatch: Reverse for ‘convertST’ with keyword arguments ‘{‘machineST’: ‘1’}’ not found. 1 pattern(s) tried: [‘app_fabric/convertST\\Z’]

What is the proper way to pass kwargs to a class based_view?

I thank you for your help

2

It’s the same as how you pass them to FBVs - through the URL.

For this to work, your url should be something like:
path('convertST/<str:machineST>/', views.ConvertST.as_view(), name='convertST'),

It’s more appropriate to set values for attributes like machine_model and machineST in the __init__ method instead of as class variables. Doing it the way you have it can create some very unpleasant side-effects.

3

Thanks for your reply. The view consertST requires 2 parameters which I dynamically collect through redirections. This means duplicating the line in the urls.py (oneline with 0 parameter, with 1 ad with 2 parameters).

what is the purpose of the kwargs argument in the path() as described here django.urls functions for use in URLconfs | Django documentation | Django

and also how can the class attribute declared in class based view can be used.

I am confused with this

I thank you for your help

4

Yep. (See the URL examples)

Or, identify a default (sentinel) value that is always supplied in the absence of an override.

Or, you could use query variables instead of url parameters.

Keep in mind that there is no “direct” connection between your use of the reverse function and the view being called. You use reverse to create a url, which is then sent to the browser. It’s that url which the browser uses to request the page. If the variable isn’t in the URL, then the view doesn’t get it.

It is described at URL dispatcher | Django documentation | Django. These would be parameters that are not supplied within the url nor overridden - they are constants for that URL.

A class attribute applies to all instances of a class. For example, if you subclass TemplateView, and assign a value to the template_name attribute, all instances of that view will use the identified template.

Example:

class MyTemplateView_1(TemplateView):
    template_name = 'template_1.html'

class MyTemplateView_2(TemplateView):
    template_name = 'template_2.html'

Every URL resolving to MyTemplateView_1 will render template_1.html.
Every URL resolving to MyTemplateView_2 will render template_2.html.

If this is not clear, then you might want to review the Python documentation on classes, and the differences between class variables and instance variables.

5

Hello Thanks for taking the time to clarify. The **initkwargs which are in the viewname.as_view() are the parameters encoded in the url?

I now have

path('convertST/<machineST>/<machine_model>', views.ConvertST.as_view(), name='convertST'),
path('convertST/<machineST>', views.ConvertST.as_view(), name='convertST'),
path('convertST', views.ConvertST.as_view(), name = 'convertST'),parameters in a dictionnary which django function will encode the get_success_url

and I have the parameters in a dictionnary.

In get_successs_url I have

return redirect(view_name, kwargs=kwargs)

and it still returns the error. How should I encode the url?

should I create the string with ? and / ???

I suspect there is a better way!….

6

get_success_url is supposed to return a string.

The redirect shortcut function returns an HttpResponseRedirect object, not a string.

For future reference, it always helps if you post the complete code with the complete error message and not try to send excerpts that may be lacking important context for understanding what’s happening. Also, copy/pasting the complete class or function reduces the possibility of introducing errors caused by a mistaken edit.