Crate 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);

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.

Structs

Entry

Ref

Reference to a resource.

RefMut

Mutable reference to a resource.

Resources

Map from TypeId to type.

Traits

Resource

Trait to represent any type that is Send + Sync + 'static.