on-get callback

[uncle-lv]

I think on_get callback may just be simple like this:

cache = Cache(on_get=on_get)

The callback function.

Callable[[key: Hashable, value: Any],  None]

In fact, I've hardly ever seen a on-get listener in cache libraries. Do we really need it? 🤷

[dgilland]

I'm also not sure on the utility of it, but the callback could also include whether the key there or not. That might make it a little more useful.

[uncle-lv]

I'm also not sure on the utility of it, but the callback could also include whether the key there or not. That might make it a little more useful.

If the key is missed, whichever is better is to set the value to None or UNSET?

[dgilland]

If the key is missed, whichever is better is to set the value to None or UNSET?

Another question around this would be whether having value always be the returned value (i.e. the existing value or the default value) and send another variable to indicate whether the key exists would be preferable over having the value only ever be the existing one. Potentially the default value could come from a default function so would having that value potentially be useful? Seems like we'd have more information with the first option.

[uncle-lv]

If the key is missed, whichever is better is to set the value to None or UNSET?

Another question around this would be whether having value always be the returned value (i.e. the existing value or the default value) and send another variable to indicate whether the key exists would be preferable over having the value only ever be the existing one. Potentially the default value could come from a default function so would having that value potentially be useful? Seems like we'd have more information with the first option.

Callable[[key: Hashable, value: Any, existed: bool],  None]

Add existed to indicate whether the key has existed. If existed is true, value is the real value. Otherwise, value is the default value.

[dgilland]

Callable[[key: Hashable, value: Any, existed: bool], None]
Add existed to indicate whether the key has existed. If existed is true, value is the real value. Otherwise, value is the default value.

👍

[dgilland]

Done in #38