Cannot overload cache drivers (memcached)

[eluser]Antoine P.[/eluser]
Hello,

I have a question about caching in CI 2.0. As I am working on a project that may involve several web sites/dev teams, I would like to overload caching driver (memcached in my case) in order to automatically add a prefix key to my cache keys, depending on an environment var previously set.

I've tried to overload the core Cache_memcached driver (libraries/Cache/drivers) but it seems cache drivers can only be replaced and not overloaded. Then, I tried to extend the core Cache library instead (libraries/with the same result.

I've found a trick which consists in modifying the CI_Driver_Library::__get method but this is not a good solution to me as it modifies my CI core.

Can someone help me please?