I have a boolean field on my model that represents whether someone has canceled their membership or not. I am trying to create a custom SimpleListFilter that allows this field to be filtered on.
However, I really want to show only those who are not canceled by default. Is there someway to select the "No" option by default? This is my filter so far:
class CanceledFilter(SimpleListFilter):
title = 'Canceled'
# Parameter for the filter that will be used in the URL query.
parameter_name = 'canceled'
def lookups(self, request, model_admin):
return (
(True, 'Yes'),
(False, 'No'),
)
def queryset(self, request, queryset):
if self.value() is True or self.value() is None:
return queryset.filter(canceled=True)
if self.value() is False:
return queryset.filter(canceled=False)
EDIT: I should have been a bit clearer. I am specifically trying to do this in the Admin interface. When I add the above filter as a list_filter in admin. I get a filter on the side of the admin page with 3 choices: All, Yes and No.
I would like the "No" choice or none of the choices to be set by default. Instead the "All" choice is always set by default. Is there some none hacky way to set the default filter choice or something like that.
Basiclly in Admin when they view the Members, I only want to show the active (not canceled) by default. If they click "All" or "Yes" then I want to show the canceled ones.
Update: Note this is the same as question Default filter in Django admin, but I that question is now 6 years old. The accepted answer is marked as requiring Django 1.4. I am not sure if that answer will still work with newer Django versions or is still the best answer.
Given the age of the answers on the other question, I am not sure how we should proceed. I don't think there is any way to merge the two.
Had to do the same and stumbled upon your question. This is how I fixed it in my code (adapted to your example):
class CanceledFilter(SimpleListFilter):
title = 'Canceled'
# Parameter for the filter that will be used in the URL query.
parameter_name = 'canceled'
def lookups(self, request, model_admin):
return (
(2, 'All'),
(1, 'Yes'),
(0, 'No'),
)
def queryset(self, request, queryset):
if self.value() is None:
self.used_parameters[self.parameter_name] = 0
else:
self.used_parameters[self.parameter_name] = int(self.value())
if self.value() == 2:
return queryset
return queryset.filter(cancelled=self.value())
Some explanation is required. The querystring is just part of the URL, and exactly what the name implies: a query string. Your values come in as strings, not as booleans or integers. So when you call self.value(), it returns a string.
If you examine the URL you get when you click on the Yes/No, when not using a custom list filter, you'll see it encodes it as 1/0, not True/False. I went with the same scheme.
For completeness and our future readers, I also added 2 for All. Without verifying, I assume that was None before. But None is also used when nothing is selected, which defaults to All. Except, in our case it needs to default to False, so I had to pick a different value. If you don't need the All option, just remove the final if-block in the queryset method, and the first tuple in the lookups method.
With that out of the way, how does it work? The trick is in realising that self.value() just returns:
self.used_parameters.get(self.parameter_name, None)
which is either a string, or None, depending on whether the key is found in the dictionary or not. So that's the central idea: we make sure it contains integers and not strings, so that self.value() can be used in the call to queryset.filter(). Special treatment for the value for All, which is 2: in this case, just return queryset rather than a filtered queryset. Another special value is None, which means there is no key parameter_name in the dictionary. In that case, we create one with value 0, so that False becomes the default value.
Note: your logic was incorrect there; you want the non-cancelled by default, but you treat None the same as True. My version corrects this.
ps: yes, you could check for 'True' and 'False' rather than True and False in your querystring method, but then you'd notice the correct selection would not be highlighted because the first elements in your tuple don't match up (you're comparing strings to booleans then). I tried making the first elements in the tuples strings too, but then I'd have to do string comparison or eval to match up 'True' to True, which is kind of ugly/unsafe. So best stick to integers, like in my example.