angular-di

Angular dependency injection uses a hierarchical injector tree to provide services to components. The modern inject() function resolves dependencies dynamically, enabling modular and maintainable application architectures.

The best way to provide a configuration object is using custom injection tokens. Injection tokens allow you to inject non-class dependencies, ensuring multiple services and components receive the exact same shared settings via useValue or useFactory providers.

You configure Angular providers by specifying useClass to map tokens to classes, useValue for static objects, useFactory for dynamic creation, and useExisting to alias tokens. This controls dependency resolution and service architecture.

Use root-provided services for singletons shared across the entire application, and scoped services for component or route-level instances. Scoped services control service lifecycle and state isolation, preventing data leakage between different feature modules.

Multi-providers allow a single injection token to resolve to an array of dependencies. By combining multi-providers with custom injection tokens, you can inject multiple values or strategies into a service, enabling extensible and dynamic provider configurations.

Yes, the inject() function supports testing strategies by allowing dynamic provider overrides in test setups. You can configure useValue or useFactory providers within test beds to mock dependencies, ensuring services are tested in isolation.