Q: Examples of Complex Data Structures?

I was wondering if there were good examples of more complex data structures, or how would I go about having an object that maintains it’s own state, where you call methods to mutate the state, like addItem(), deleteItem().

This way it can maintain to various components that subscribe to the data, need to use it to render their view, and that state could even be sync back to a server as needed, but would maintain it’s state also locally.