unity is componant system, so how can i send messages?

what i mean by this is that with componants is that you can add and remove part at runtime , making each object more flexable.,
i am using sendmessage for a few parts of my code
i want to send messages and have a return type or something to see if that message has been picked up , how do i do this part?

Messages are only one way to interact between components / scripts. Messages are always one way. The receiving script could send a message back, but usually you can just use direct references between two or more scripts and simply call a function of another component. There you can have a return type.

See this question or this one which is actually the same as yours.