Dependency Injection creating new object everytime an api is called

Question

Everytime I'm calling an api in inversify-express server the dependency is creating a new object everytime

var kernel=new Kernel();
kernel.bind<interfaces.Controller>(TYPE.Controller).to(SyncController).whenTargetNamed(TAGS.SyncController);
kernel.bind<DB_SyncDataDAO>(TYPES.DB_SyncDataDAO).to(DB_SyncDataDAO_Impl);
kernel.bind<SyncService>(TYPES.SyncService).to(SyncService_Impl);

Whenever I'm calling an api it is creating new object of each dependency everytime

Did you solve this problem? Can you you post an answer or flag the one of the answers below as valid? — Remo H. Jansen, Dec 02 '16 at 09:44

score 0 · Answer 1 · answered Oct 12 '16 at 10:50

I assume that you want some of the dependencies in your object graph to be singletons. You can do that using inSingletonScope when declaring a binding:

kernel.bind<interfaces.Controller>(TYPE.Controller)
      .to(SyncController)
      .whenTargetNamed(TAGS.SyncController)
      .inSingletonScope();

kernel.bind<DB_SyncDataDAO>(TYPES.DB_SyncDataDAO)
      .to(DB_SyncDataDAO_Impl)
      .inSingletonScope();

kernel.bind<SyncService>(TYPES.SyncService)
      .to(SyncService_Impl)
      .inSingletonScope();

As a side note (not related to your question) if DB_SyncDataDAO_Impl is an instance (nota class) then you should use

kernel.bind<T>("T").toConstantValue(instanceOfT)

Instead of:

kernel.bind<T>("T").to(classWhichIsAnImplementationOfT)

When you use toConstantValue, inSingletonScope is not required because constant values behave as singletons by default.

Hope it helps :)

Dependency Injection creating new object everytime an api is called

1 Answers1