Question

I have written a decorator to display success message on object creation:

from django.contrib import messages

def success_message(klass):
    def form_valid(self, form):
        response = super(klass, self).form_valid(form)
        messages.success(self.request, 'Object added successfully')
        return response

    klass.form_valid = form_valid
    return klass

and use it to decorate class based generic view:

@success_message
class BandCreateView(CreateView):
    model = Band

Now I want to parameterize the decorator so this is possible:

@success_message('Band created successfully.')
class BandCreateView(CreateView):
    model = Band

How do I do it? I tried adding message parameter to success_message but the compiler complained about parameter count mismatch so I figure there must be another way.

Answer 1

Looks like you have to use closure:

def decorator(arg):
    def wrap(klass): ...
    return wrap

because your call is evaluated to

class BandCreateView(CreateView): ...
BandCreateView = @success_message('Band created successfully.')(BandCreateView)

note double call