interfacebased

Interface based communication

The name of this way of communicating is in lack of a better name. The idea with this kind of architecture is to pass interfaces around, and to invoke methods or whatever is suitable in the appropriate places. This is one of the methods that I have been using more and more lately.

The idea

MainViewModel is the glue between IFriendsViewModel and IHairColorCountingViewModel. So, each IFriendViewModel has to tell MainViewModel that its hair color has changed, that way it can tell HairColorCountingViewModel to reevaluate.

MainViewModel should implement an interface that is passed down to FriendsViewModel, that will pass it to each FriendViewModel. That way, each FriendViewModel can tell MainViewModel that it should reevaluate.

How did I implement it?

Created an interface called IHandleFriendChanged and created a void OnFriendChanged in the interface.

Implemented IHandleFriendChanged in MainViewModel. OnFriendChanged is now running HairCountingViewModel.EvaluateFriendsWithBlackHair.

Expanded Initialize with IHandleFriendChanged argument.

Passed the instance of MainViewModel to FriendsViewModel.Initialize.

Expanded constructor of FriendViewModel with IHandleFriendChanged.

Send IHandleFriendChanged in FriendsViewModel.Initialize to each FriendViewModel.Initialize.

Saved IHandleFriendChanged to a backing store in FriendViewModel.

Run OnFriendChanged in HairColor setter.

Summary

I like this way of communication much better than event based communication. It is much easier to follow now, as we can get a sense of who is implementing it, who is referring the interface and where it is running the different methods that the interface has. It also feels like we have some more flexibility as we can very easily send arguments, without any overhead like when we are dealing with events.