coi

Dependency Injection in Rust

The goal of this crate is to provide a simple dependency injection framework that is easy to use. Performance is not an initial concern, but might be later on as the crate matures.

Example

use coi::{container, Inject};
use std::sync::Arc;

// Inherit `Inject` on all traits you'd like to inject
pub trait Trait1: Inject {
    fn describe(&self) -> &'static str;
}

// derive `Inject` on all structs that will provide the implementation
#[derive(Inject)]
#[coi(provides dyn Trait1 with Impl1)]
struct Impl1;

// actually impl the trait
impl Trait1 for Impl1 {
    fn describe(&self) -> &'static str {
        "I'm impl1!"
    }
}

pub trait Trait2: Inject {
    fn deep_describe(&self) -> String;
}

#[derive(Inject)]
#[coi(provides dyn Trait2 with Impl2::new(trait1))]
struct Impl2 {
    // inject dependencies by Arc<dyn SomeTrait>
    #[coi(inject)]
    trait1: Arc<dyn Trait1>,
}

impl Impl2 {
    fn new(trait1: Arc<dyn Trait1>) -> Self {
        Self { trait1 }
    }
}

impl Trait2 for Impl2 {
    fn deep_describe(&self) -> String {
        format!("I'm impl2! and I have {}", self.trait1.describe())
    }
}

// It even works on structs
#[derive(Debug, Inject)]
#[coi(provides JustAStruct with JustAStruct)]
pub struct JustAStruct;

fn main() {
    // Then construct your container with the helper `container!` macro
    let container = container!{
        trait1 => Impl1Provider,
        trait2 => Impl2Provider; scoped,
        struct => JustAStructProvider; singleton
    };

    // And resolve away!
    let trait2 = container
        .resolve::<dyn Trait2>("trait2")
        .expect("Should exist");
    println!("Deep description: {}", trait2.as_ref().deep_describe());
    let a_struct = container
        .resolve::<JustAStruct>("struct")
        .expect("Should exist");
    println!("Got struct! {:?}", a_struct);
}

Name

The name coi comes from an inversion of the initialism IoC (Inversion of Control).

License

SPDX-License-Identifier: MIT OR Apache-2.0