Logi-DX Injection

The purpose of this library is rather simplistic in the sense that it's designed to simply enable typescript applications to use some degree of dependency injection through the use of a series of decorators.

Inject

The @Inject decorator is intended to decorate class properties, just to help clear up the likes of any mess that might accumulate within the constructor & so on.

An example of how you might consume this might look something along the lines of:

interface IUsersRepository {
    // Some interface for the users repository.
}

@Injectable()
class UsersRepository implements IUsersRepository {
    // Some code associated with users & persistent storage.
}

class UsersController {
    @Inject(UsersRepository)
    private repo: IUsersRepository;
}

Injectable

Since the example above references, I thought it might be wise to simply specify the intention of this decorator. The @Injectable decorator is intended to be a class decorator, in doing so, you're informing the IOC container that a given class can be injected elsewhere in the code base.

Singleton

The @Singleton decorator is very similar to the @Injectable decorator, the difference being that you're informing the IOC container that you'd like to create the given dependency as a singleton as opposed to creating a new instance of the class every time you want to reference the given dependency.

interface IUserManager {
    addUser(): void;
    removeUser(): void;
    countUsers(): number
}

@Singleton()
class UserManager implements IUserManager {
    // Some silly example. 
    private userCount: number;

    public constructor() {
        this.userCount = 0;
    }

    public addUser(): void {
        this.userCount ++;
    }

    public removeUser(): void {
        this.userCount --;
    }

    public countUsers(): number {
        return this.userCount;
    }
}

class Application {
    @Inject(UserManager)
    private manager: IUserManager;
    
    public main() {
        manager.addUser();
        manager.addUser();
        console.log('Example #1', manager.countUsers());
    }
}

class Demo {
    @Inject(UserManager)
    private manager: IUserManager;
    
    public main() {
        manager.addUser();
        manager.addUser();
        console.log('Example #2', manager.countUsers());
    }
}

// Just to run the above code. 
new Application().main();
new Demo().main();