Inject
A parameter decorator on a dependency parameter of a class constructor that specifies a custom provider of the dependency.
| Option | Description |
|---|---|
token
|
A DI token that maps to the dependency to be injected. |
Description
Learn more in the "Dependency Injection Guide".
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);