borrow-bag

A type-safe, heterogeneous collection with zero-cost add and borrow.

BorrowBag allows the storage of any value, and returns a Handle which can be used to borrow the value back later. As the BorrowBag is add-only, Handle values remain valid for the lifetime of the BorrowBag.

For usage details, please see the documentation

Motivation

Initially, BorrowBag was conceived to solve the problem of storing concrete types implementing a certain trait, without losing their type information, and with an ability to borrow them back later.

The original implementation was generic enough that it was immediately extracted into this crate.

Use cases

Please create an issue or pull request so your use case can be added here.

Example

extern crate borrow_bag;

use borrow_bag::new_borrow_bag;

struct X(u8);
struct Y(u8);

fn main() {
    let bag = new_borrow_bag();
    let (bag, x_handle) = bag.add(X(1));
    let (bag, y_handle) = bag.add(Y(2));

    let x: &X = bag.borrow(x_handle);
    assert_eq!(x.0, 1);
    let y: &Y = bag.borrow(y_handle);
    assert_eq!(y.0, 2);
}

Contributing

Bug reports and feature requests

Issues welcome.

Development

Contributions welcome via pull request.

Requested contributions

• Code review
• Feedback and/or criticism on the use of types
• Further validation that this is in fact "zero-cost" (when optimised)

License

MIT