Inject

A parameter decorator on a dependency parameter of a class constructor that specifies a custom provider of the dependency.

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Option	Description
token	A DI token that maps to the dependency to be injected.

Description

Learn more in the "Dependency Injection Guide".

Options

token
A DI token that maps to the dependency to be injected.
token: any

Usage notes

The following example shows a class constructor that specifies a custom provider of a dependency using the parameter decorator.

class Engine {}

@Injectable()
class Car {
  constructor(@Inject('MyEngine') public engine: Engine) {}
}

const injector =
    ReflectiveInjector.resolveAndCreate([{provide: 'MyEngine', useClass: Engine}, Car]);

expect(injector.get(Car).engine instanceof Engine).toBe(true);

When @Inject() is not present, the injector uses the type annotation of the parameter as the provider.

class Engine {}

@Injectable()
class Car {
  constructor(public engine: Engine) {
  }  // same as constructor(@Inject(Engine) engine:Engine)
}

const injector = ReflectiveInjector.resolveAndCreate([Engine, Car]);
expect(injector.get(Car).engine instanceof Engine).toBe(true);