Macro shaku::module

module!() { /* proc-macro */ }

Create a Module which is associated with some components and providers.

Builder

A fn builder(submodules...) -> ModuleBuilder<Self> associated function will be created to make instantiating the module convenient. The arguments are the submodules the module uses.

Module interfaces

After the module name, you can add : MyModuleInterface where MyModuleInterface is the trait that you want this module to implement (ex. trait MyModuleInterface: HasComponent<MyComponent> {}). The macro will implement this trait for the module automatically. That is, it is the same as manually adding the line: impl MyModuleInterface for MyModule {}. See MyModuleImpl in the example below. See also ModuleInterface.

Submodules

A module can use components/providers from other modules by explicitly listing the interfaces from each submodule they want to use. Submodules can be abstracted by depending on traits instead of implementations. See MySecondModule in the example below.

See also the submodules getting started guide.

Generics

This macro supports generics at the module level:

use shaku::{module, Component, Interface, HasComponent};

trait MyComponent<T: Interface>: Interface {}

#[derive(Component)]
#[shaku(interface = MyComponent<T>)]
struct MyComponentImpl<T: Interface + Default> {
    value: T
}
impl<T: Interface + Default> MyComponent<T> for MyComponentImpl<T> {}

// MyModuleImpl implements Module and HasComponent<dyn MyComponent<T>>
module! {
    MyModule<T: Interface> where T: Default {
        components = [MyComponentImpl<T>],
        providers = []
    }
}

Circular dependencies

This macro will detect circular dependencies at compile time. The error that is thrown will be something like "overflow evaluating the requirement TestModule: HasComponent<(dyn Component1Trait + 'static)>".

It is still possible to compile with a circular dependency if the module is manually implemented in a certain way. In that case, there will be a panic during module creation with more details.

Lazy Components

Components can be lazily created by annotating them with #[lazy] in the module declaration. The component will not be built until it is required, such as when resolve_ref is called for the first time.

use shaku::{module, Component, Interface};

trait Service: Interface {}

#[derive(Component)]
#[shaku(interface = Service)]
struct ServiceImpl;
impl Service for ServiceImpl {}

module! {
    MyModule {
        components = [#[lazy] ServiceImpl],
        providers = []
    }
}

Examples

use shaku::{module, Component, Interface, HasComponent};

trait MyComponent: Interface {}
trait MyModule: HasComponent<dyn MyComponent> {}

#[derive(Component)]
#[shaku(interface = MyComponent)]
struct MyComponentImpl;
impl MyComponent for MyComponentImpl {}

// MyModuleImpl implements Module, MyModule, and HasComponent<dyn MyComponent>
module! {
    MyModuleImpl: MyModule {
        components = [MyComponentImpl],
        providers = []
    }
}

// MySecondModule implements HasComponent<dyn MyComponent> by using
// MyModule's implementation.
module! {
    MySecondModule {
        components = [],
        providers = [],

        use MyModule {
            components = [MyComponent],
            providers = []
        }
    }
}