🗂️ resman

Runtime managed resource borrowing.

This library provides a map that can store one of any type, as well as mutable borrows to each type at the same time.

Note: This implementation is extracted from shred, with the following differences:

• Uses downcast-rs instead of mopa for downcasting types.
• Adds Debug and PartialEq implementations for borrow types when the resource type implements those traits.
• Returns None instead of panicking for try_borrow* functions when the resource is already borrowed.

Usage

Add the following to Cargo.toml

resman = "0.1.0"

In code:

use resman::Resources;

struct A(u32);
struct B(u32);

fn main() {
    let mut resources = Resources::default();

    resources.insert(A(1));
    resources.insert(B(2));

    // We can validly have two mutable borrows from the `Resources` map!
    let mut a = resources.borrow_mut::<A>();
    let mut b = resources.borrow_mut::<B>();
    a.0 = 2;
    b.0 = 3;

    // We need to explicitly drop the A and B borrows, because they are runtime
    // managed borrows, and rustc doesn't know to drop them before the immutable
    // borrows after this.
    drop(a);
    drop(b);

    // Multiple immutable borrows to the same resource are valid.
    let a_0 = resources.borrow::<A>();
    let _a_1 = resources.borrow::<A>();
    let b = resources.borrow::<B>();

    println!("A: {}", a_0.0);
    println!("B: {}", b.0);

    // Trying to mutably borrow a resource that is already borrowed (immutably
    // or mutably) returns `None`.
    let a_try_borrow_mut = resources.try_borrow_mut::<A>();
    let exists = if a_try_borrow_mut.is_some() {
        "Some(..)"
    } else {
        "None"
    };
    println!("a_try_borrow_mut: {}", exists); // prints "None"
}

See Also

• anymap: Map of any type, without multiple mutable borrows.
• shred: Contains Resources type, plus a task dispatcher.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.