Why are KeyConstructor bits class variables about drf-extensions HOT 6 CLOSED

Hi.

I am wondering why the KeyConstructor bits are class variables not instance?

Why? Instances of what? As I see they are instances. For example:

class DefaultKeyConstructor(KeyConstructor):
    unique_method_id = bits.UniqueMethodIdKeyBit()
    format = bits.FormatKeyBit()
    language = bits.LanguageKeyBit()

unique_method_id - is instance of bits.UniqueMethodIdKeyBit.

I think it's a good idea to allow to send custom params attribute in KeyConstructor initialization method, but it brings some complexity. For example, if you send params={'request_meta': ['GEOIP_COUNTRY']}, what about other key bits? Should they use default params, or fail without their custom params?

You can rewrite your example code with simple class inheritance:

class CityView(views.APIView):
    @cache_response(key_func=CityGetKeyConstructor())
    def get(self, request, *args, **kwargs):
        ...

class CountryGetKeyConstructor(CityView):
    request_meta = RequestMetaKeyBit(['GEOIP_COUNTRY'])

class CountryView(views.APIView):
    @cache_response(key_func=CountryGetKeyConstructor())
    def get(self, request, *args, **kwargs):
        ...

But anyway, i think it's a good idea that needs more planning. I would love to review pull request or see more of your use cases.

from drf-extensions.

Yes, but each instance of DefaultKeyConstructor shares the same instances of the KeyBits. If you use the same KeyConstructor in two different places, you cant change the parameters of it's KeyBits.

My actual use case is a little different (similar to the CustomListKeyConstructor in your docs).

class CustomListKeyConstructor(DefaultKeyConstructor):
    def __init__(self, models):
        self.model_bit = UpdatedAtKeyBit(models)
        super(CustomListKeyConstructor, self).__init__()

Where UpdatedAtKeyBit checks a updated_at key. Currently this will not work because DefaultKeyConstructor only looks in dir(self.__class__), and I wondered if this was by design

Thanks

from drf-extensions.

You can try to alter self.bits in __init__ method:

class CustomListKeyConstructor(DefaultKeyConstructor):
    def __init__(self, models):
        super(CustomListKeyConstructor, self).__init__()
        self.bits['model_bit'] = UpdatedAtKeyBit(models)

from drf-extensions.

Great, thanks. Do you think caching based on model last-modified is a common enough use case to provide a KeyConstuctor?

from drf-extensions.

Absolutely. I'm going to implement KeyConstructor params attribute in next two days and i think it will be a better approach than such kind of __init__ redefinition.

By the way, don't forget to use *args and **kwargs in super invocation.

class CustomListKeyConstructor(DefaultKeyConstructor):
    def __init__(self, models, *args, **kwargs):
        super(CustomListKeyConstructor, self).__init__(*args, **kwargs)
        self.bits['model_bit'] = UpdatedAtKeyBit(models)

from drf-extensions.

I've implemented KeyConstructor params attribute http://chibisov.github.io/drf-extensions/docs/#key-constructor-params

from drf-extensions.