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In Django, a models’ manager is the object through which models perform database queries. Each Django model has at least one manager, which is objects
, and you can create your own to change the default behavior.
So, your statement
But these functions could also be placed in the Model too
Well, not really because the model is still depending on the default manager to retrieve the queryset.
Let me try to explain in terms of an example. Lets say your application requires a model object to show only objects with a status of published
. Now, MyModel.objects.all()
retrieves everything, and you would have to specify the filter MyModel.objects.filter(published=True)
every single time.
Now, you can override this default behavior.
class MyModelAdmin(admin.ModelAdmin):
def queryset(self, request):
return MyModel.objects.filter(published=True)
What we just did was override the default behaviour of the default manager.
Now, lets say you want everything, You can do something like
class MyModelAdmin(admin.ModelAdmin):
def queryset(self, request):
return MyModel.objects.filter(published=True)
def all_objects(self, request):
return MyModel.objects.all()
and while accessing all objects, just do
MyModel.objects.all_objects()
It is also possible to have multiple managers to a single model
In short, managers give a lot of flexibility in terms of accessing querysets to the model.