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<h1>nject</h1>
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<br />
Simple zero cost dependency injection library made for rust
## Install
Add the following to your `Cargo.toml`:
```toml
[dependencies]
nject = "0.3"
```
## Why `nject`?
- **Zero cost**: Using this library is equivalent to manually injecting your dependencies as shown in the [benchmarks](https://github.com/nicolascotton/nject/tree/main/examples/benchmark).
- **Compile time only**: If configured incorrectly, `nject` will fail at compile time.
## Use cases
### Removes the need to specify dependencies across your modules
```rust
use nject::{injectable, provider};
#[injectable]
struct DepOne;
#[injectable]
struct DepTwo {
dep: DepOne,
}
#[injectable]
struct Facade {
dep: DepTwo,
}
#[provider]
struct Provider;
fn main() {
let _facade: Facade = Provider.provide();
}
```
### Works with lifetimes - enables shared dependencies
```rust
use nject::{injectable, provider};
struct DepOne;
#[injectable]
struct Facade<'a> {
dep: &'a DepOne,
}
#[provider]
struct Provider<'a> {
#[provide]
shared: &'a DepOne,
}
fn main() {
let provider = Provider { shared: &DepOne };
let _facade: Facade = provider.provide();
}
```
### Works with dyn traits
```rust
use nject::{injectable, provider};
trait Greeter {
fn greet(&self);
}
#[injectable]
struct GreeterOne;
impl Greeter for GreeterOne {
fn greet(&self) {
println!("Greeting");
}
}
#[injectable]
struct Facade<'a> {
boxed_dep: Box<dyn Greeter>,
ref_dep: &'a dyn Greeter,
}
#[provider]
#[provide(Box<dyn Greeter>, Box::<GreeterOne>::new(self.provide()))]
struct Provider {
#[provide(dyn Greeter)]
greeter: GreeterOne,
}
fn main() {
let provider = Provider { greeter: GreeterOne };
let _facade: Facade = provider.provide();
}
```
### Works with generics
```rust
use nject::{injectable, provider};
#[injectable]
struct DepOne;
#[injectable]
struct Facade<T> {
dep: T,
}
#[provider]
struct Provider;
fn main() {
let _facade: Facade<DepOne> = Provider.provide();
}
```
### Works with generic providers
```rust
use nject::{injectable, provider};
trait Greeter {
fn greet(&self);
}
#[injectable]
struct DevGreeter;
impl Greeter for DevGreeter {
fn greet(&self) {
println!("Greeting Dev");
}
}
#[injectable]
struct ProdGreeter;
impl Greeter for ProdGreeter {
fn greet(&self) {
println!("Greeting production");
}
}
#[injectable]
struct Facade<'a> {
dep: &'a dyn Greeter,
}
#[provider]
struct Provider<'a, T: Greeter>(#[provide(dyn Greeter)] &'a T);
fn main() {
let _dev_facade: Facade = Provider(&DevGreeter).provide();
let _prod_facade: Facade = Provider(&ProdGreeter).provide();
}
```
### Easily inject non-injectable dependencies
```rust
use nject::{inject, injectable, provider};
#[inject(Self { non_injectable_value: 123 })]
struct InjectableFromInjectAttr {
non_injectable_value: i32,
}
struct NonInjectable {
non_injectable_value: i32,
}
#[inject(Self {
non_injectable_value: injectable_dep.non_injectable_value + 10,
injectable_dep
}, injectable_dep: InjectableFromInjectAttr)]
struct PartiallyInjectable {
non_injectable_value: i32,
injectable_dep: InjectableFromInjectAttr
}
#[injectable]
struct Facade {
dep_from_injected: InjectableFromInjectAttr,
dep_from_partial_inject: PartiallyInjectable,
#[inject(NonInjectable { non_injectable_value: 456 })]
dep_from_inject_attr: NonInjectable,
#[inject(InjectableFromInjectAttr { non_injectable_value: 789 })]
dep_from_inject_attr_override: InjectableFromInjectAttr,
#[inject(PartiallyInjectable {
non_injectable_value: 111,
injectable_dep
}, injectable_dep: InjectableFromInjectAttr)]
dep_from_partial_inject_attr_override: PartiallyInjectable,
}
#[provider]
struct Provider;
fn main() {
let _facade = Provider.provide::<Facade>();
}
```
### Use modules to export internal shared dependencies
```rust
use nject::{injectable, provider};
mod sub {
use nject::{injectable, module};
trait Greeter {
fn greet(&self) -> &str;
}
#[injectable]
struct GreeterOne;
impl Greeter for GreeterOne {
fn greet(&self) -> &str {
"One"
}
}
#[injectable]
struct InternalType(#[inject(123)] i32); // Not visible outside of module.
#[injectable]
pub struct Facade<'a> {
hidden: &'a InternalType,
hidden_dyn: &'a dyn Greeter
}
#[injectable]
#[module]
pub struct Module {
#[export]
hidden: InternalType,
#[export(dyn Greeter)]
hidden_dyn: GreeterOne
}
}
#[injectable]
#[provider]
struct Provider {
#[import]
sub_mod: sub::Module
}
fn main() {
#[provider]
struct InitProvider;
let provider = InitProvider.provide::<Provider>();
let _facade = provider.provide::<sub::Facade>();
}
```
#### Limitations
1. Dependencies can only be exported by a single module.
1. Modules can only export types defined in its crate.
1. Generic parameters are not supported on modules.
## Examples
You can look into the [axum](https://github.com/nicolascotton/nject/tree/main/examples/axum)/[actix](https://github.com/nicolascotton/nject/tree/main/examples/actix) example for a Web API use case or into the [Leptos](https://github.com/nicolascotton/nject/tree/main/examples/leptos) example for a Web App.
## Credits
- [Syn](https://github.com/dtolnay/syn) - [MIT](https://github.com/dtolnay/syn/blob/master/LICENSE-MIT) or [Apache-2.0](https://github.com/dtolnay/syn/blob/master/LICENSE-APACHE)
- [Quasi-Quoting](https://github.com/dtolnay/quote) - [MIT](https://github.com/dtolnay/quote/blob/master/LICENSE-MIT) or [Apache-2.0](https://github.com/dtolnay/quote/blob/master/LICENSE-APACHE)
- [Rust](https://github.com/rust-lang/rust) - [MIT](https://github.com/rust-lang/rust/blob/master/LICENSE-MIT) or [Apache-2.0](https://github.com/rust-lang/rust/blob/master/LICENSE-APACHE)