Lazy injection

Lazy injection allows you to defer the creation of services, by returning a function instead. When invoked, this function will create the service on demand. Lazy injection could aso be a solution to enable circular dependencies.

Usage

In order to use lazy injection, just pass { lazy: true }:

import { inject } from "@needle-di/core";
import { FooService } from "./foo.service";

class MyService {
  constructor(
    private fooService = inject(FooService, { lazy: true }),
  ) {}
  
  public doSomething() {
    // invoking the function will trigger the creation of `FooService`
    this.fooService().someMethod();
  }
}

Rules and behaviour

• Lazy injection can be combined with optional injection. In that case, it would the function above would be () => FooService | undefined;
• Lazy injection can also be combined with async injection. In that case, it would the function above would be () => Promise<FooService>;