Inversifyjs: How to bind a singleton for two different interfaces

[CowboyBebug]

Hi. I have a class, implementing multiple interfaces:

export class InMemoryFoodLogRepository implements IAddFoodLog, IGetFoodLogs {
}

This is a repository for, obviously, some food logs. So it should be a singleton (or else would insert everything happily and forget about them in a second). with below code

container.bind<IAddFoodLog>(TYPES.AddFoodLog).to(InMemoryFoodLogRepository).inSingletonScope();

I was able to use IAddFoodLog interface consistently and things will be saved in InMemoryFoodLogRepository. But when I want to fetch them with IGetFoodLogs interface, I find that inversify will create another instance of InMemoryFoodLogRepository for the new interface.

container.bind<IAddFoodLog>(TYPES.AddFoodLog).to(InMemoryFoodLogRepository).inSingletonScope();
container.bind<IGetFoodLogById>(TYPES.GetFoodLogById).to(InMemoryFoodLogRepository).inSingletonScope();

So how could I do this?

[bodograumann]

What I currently do, but which seems a little ugly, is the following:

container
  .bind<IAddFoodLog & IGetFoodLogById>(TYPES.AddFoodLog)
  .to(InMemoryFoodLogRepository).inSingletonScope();
const foodLogInstance = container.get<IAddFoodLog & IGetFoodLogById>(TYPES.AddFoodLog);
container
  .bind<IGetFoodLogById>(TYPES.GetFoodLogById)
  .toConstantValue(foodLogInstance);

[miroslavvojtus]

To impelement SOLID and espetially Interface segregation it would be nice to have such a feature.

const A = Symbol("A");
interface A {
  fnA(): void;
}
const B = Symbol("B");
interface B {
  fnB(): void;
}

class ComplexLegacyAB implements A, B {
  // ...
}

// in module registration
// internal
bind<ComplexLegacyAB>(ComplexLegacyAB).toSelf().inSingletonScope();

// exposed
bind<A>(A).to(ComplexLegacyAB); // should poitn to the same singleton;
bind<B>(B).to(ComplexLegacyAB); // should poitn to the same singleton;

Now I have to create implementations for A and B which delegates the calls to ComplexLegacyAB what is annoying espetially when there are dozen of implemented interfaces.
If I could inject the ComplexLegacyAB instance by the interface it would allow me to step by step separate the legacy code.

[bodograumann]

Have you tried using transitive bindings?

[mcshaz]

Have you tried using transitive bindings?

@bodograumann - can you please give an example of how the code you posted on the 9th Jan would look using transitive bindings? Thank you

[bodograumann]

@mcshaz, of the top of my head, it should work like this:

container
  .bind<IAddFoodLog & IGetFoodLogById>(TYPES.AddFoodLog)
  .to(InMemoryFoodLogRepository)
  .inSingletonScope();
container
  .bind<IGetFoodLogById>(TYPES.GetFoodLogById)
  .toService(TYPES.AddFoodLog);

Personally I am now using abstract base classes as service identifiers so that I don’t have to provide the generic type parameters in order for type checking to work properly.
So the type parameters might need to be adjusted.

[smac89]

Have you tried using container.bind.toConstantValue?