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resman

Runtime managed resource borrowing

5 releases (breaking)

0.5.0 Aug 8, 2021
0.4.0 Aug 1, 2021
0.3.0 Jun 28, 2021
0.2.0 Jun 27, 2021
0.1.0 Apr 11, 2021

#3 in #share

26 downloads per month

MIT/Apache

28KB
515 lines

🗂️ resman

Crates.io CI Coverage Status

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 = "0.5.0"

# or
resman = { version = "0.5.0", features = ["debug"] }

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"
}

Features

  • "debug":

    The Debug implementation for Resources will use the Debug implementation for the values when printed. This requires that all Resources to also implement Debug.

    Given the following:

    let mut resources = Resources::default();
    resources.insert(1u32);
    println!("{:?}", resources);
    

    Without "debug" feature:

    {TypeId { t: 12849923012446332737 }: ".."}
    

    With "debug" feature:

    {TypeId { t: 12849923012446332737 }: 1}
    

See Also

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

License

Licensed under either of

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.

Dependencies

~74KB