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#132 in Memory management

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Used in 52 crates (9 directly)


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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 doesn't have any 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.


use generational_box::{UnsyncStorage, AnyStorage};

// Create an owner for some state for a scope
let owner = UnsyncStorage::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");

How it works

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


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