i have a deployer put seeds in the composter and another one which will release the bone meal from the composter. when the composter is full, the bone meal is released and the composter is empty, but the deployer doesn't put seeds in it

use hoppers or funnels/extractors

It looks like you want to be able to automatically empty a deployers hand. From my testing, this is not possible. What you can do in your case is just use vanilla hoppers above and below the compost er. No deployers needed.

On what

Extracting from deployers works as of v0.2.2b
Issue can be closed.