The Observer pattern, quite simply, lets one component notify other components that something happened. The pattern is used all over the place: for example, when binding data to UI, we can program domain objects such that, when they change, they generate notifications that the UI can subscribe to and update the visuals. On the other hand, editing data in the UI should modify data behind the scenes, which requires the reverse set of operations to occur.
Events
The Observer pattern is a popular and necessary ...
