Storing Application State

This page covers several ways that a programmer can store the state of the application.

Single Silo Method

This is perhaps the easiest method to understand, and works best for small applications that do no require a large amount of state to be remembered. The idea behind this method is simple: “One struct for all state”, and whenever a component requires knowledge about the state of the application, it requests a reference to the app state.

This is the method used in the tutorial.

Pros

This is conceptually very easy to understand. All of your states are stored in one place, and passing it to sub-components is simple.

Cons

However, you can tell when your application has outgrown the single silo application state when you begin to write code like this:

        let selected_item = &app.states.history.transacts_list.items[app.states.history.transacts_list.state.selected().unwrap()];

Another downside to this method, is the lack of multithreaded support. If you begin to use multiple threads that need access to the application state, access to the app can become a bottleneck as Mutex and locks get handed around.