A constructor parameter decorator that marks a dependency as optional.

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See also

• "Dependency Injection Guide".

Description

The DI framework provides null if the dependency is not found. For example, the following code allows the possibility of a null result:

class Engine {}

@Injectable()
class Car {
  constructor(@Optional() public engine: Engine) {}
}

const injector = ReflectiveInjector.resolveAndCreate([Car]);
expect(injector.get(Car).engine).toBeNull();

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