dioxus/packages/generational-box/README.md

Generational Box

Generational Box is a runtime for Rust that allows any static type to implement Copy. It can be combined with a global runtime to create an ergonomic state solution like dioxus-signals. This crate contains no unsafe code.

Three main types manage state in Generational Box:

• Store: Handles recycling generational boxes that have been dropped. Your application should have one store or one store per thread.
• Owner: Handles dropping generational boxes. The owner acts like a runtime lifetime guard. Any states that you create with an owner will be dropped when that owner is dropped.
• GenerationalBox: The core Copy state type. The generational box will be dropped when the owner is dropped.

Example:

// Create a store for this thread
let store = Store::default();

{
    // Create an owner for some state for a scope
    let owner = store.owner();

    // Create some non-copy data, move it into a owner, and work with copy data
    let data: String = "hello world".to_string();
    let key = owner.insert(data);
    
    // The generational box can be read from and written to like a RefCell
    let value = key.read();
    assert_eq!(*value, "hello world");
}
// Reading value at this point will cause a panic

How it works

Internally, generational-box creates an arena of generational RefCell's that are recyled when the owner is dropped. You can think of the cells as something like &'static RefCell<Box<dyn Any>> with some a generational check to make recyling a cell easier to debug. Then GenerationalBox's are Copy because the &'static pointer is Copy