seldom_singleton

seldom_singleton adds a helper SystemParam for when you have a resource containing a handle. If you're using Bevy's asset system to, for example, load a list of items in the game and their properties, you'd end up with a handle in a resource, and you'd need to get Res<Assets<MyItems>> to get the asset you need. This crate adds a helper that lets you avoid the additional system param.

This is a very small crate. You can just copy the source code into your project to avoid adding a dependency.

Before:

#[derive(Asset, TypePath)]
struct MyAsset;

#[derive(Resource, Deref)]
struct MySingleton(Handle<MyAsset>);

fn my_system(my_assets: Res<Assets<MyAsset>>, my_singleton: Res<MySingleton>) {
    // Return if the asset doesn't exist
    let Some(my_asset) = my_assets.get(&**my_singleton) else {
        return;
    };

    // or panic
    let my_asset = my_assets.get(&**my_singleton).unwrap();
}

After:

#[derive(Asset, TypePath)]
struct MyAsset;

// Your resource. Add it to the world yourself.
#[derive(Resource, Deref)]
struct MySingleton(Handle<MyAsset>);

// `AssetSingleton` is this crate's `SystemParam`. This type definition can help reduce boilerplate
// a bit, but it's optional. There's also `AssetSingletonMut`.
type MySingletonParam<'w> = AssetSingleton<'w, MySingleton>;

fn my_system(my_singleton: MySingletonParam) {
    // Return if the asset doesn't exist
    let Some(my_asset) = my_singleton.get() else {
        return;
    };

    // or panic
    let my_asset = my_singleton.unwrap();

    // `MySingletonMut` has `get_mut` and `unwrap_mut`
}

Usage

Add to your Cargo.toml

# Replace * with your desired version

[dependencies]
seldom_singleton = "*"

Compatibility

License

seldom_singleton is dual-licensed under MIT and Apache 2.0 at your option.

Contributing

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.