@ddd-master/query-bus package

The @ddd-master/query-bus package is a TypeScript library that provides an implementation of the query bus pattern for Domain-Driven Design (DDD) applications. It enables you to execute queries and retrieve query results in a centralized and efficient manner.

Installation

You can install the @ddd-master/query-bus package using npm:

npm install @ddd-master/query-bus

Usage

To use the @ddd-master/query-bus package, you need to define your queries and query handlers.

Defining Queries

Queries represent requests for information or data retrieval. You can define a query by implementing the IQuery interface. For example:

export interface IFindUserQuery extends IQuery {
  email: string;
}

export class FindUserQuery implements IFindUserQuery {
  public readonly email: string;

  public constructor({ email }: IFindUserQuery) {
    this.email = email;
  }
}

Defining Query Handlers

Query handlers are responsible for executing queries and returning the query results. You can implement the IQueryHandler interface to define your query handlers. For example:

export class FindUserQueryHandler implements IQueryHandler<IFindUserQuery, FindUserQueryHandlerResult> {
  private readonly userRepository: UserRepository;
  public constructor({ userRepository }: Dependencies) {
    this.userRepository = userRepository;
  }

  public handle(query: IQuery): FindUserQueryHandlerResult {
    const { email } = query as IFindUserQuery;

    const user = this.userRepository.getByEmail({ email });

    if (!user) {
      throw new Error('User not found');
    }

    return { user };
  }
}

Registering Query Handlers

Once you have your query handlers, you need to register them with the query bus. For example:

const queryBus = new QueryBus();
const findUserQueryHandler = new FindUserQueryHandler();
queryBus.register(FindUserQuery, findUserQueryHandler);

Executing Queries

To execute a query, you can use the execute method of the query bus. For example:

const result = queryBus.execute<IFindUserQuery, FindUserQueryHandlerResult>(
  new FindUserQuery({ email: 'test@gmail.com' }),
);

const { user } = result;
console.log(user);

The execute method returns the query result. You can access the result and process it accordingly.

Contributing

Contributions to the @ddd-master/query-bus package are welcome! Feel free to open issues or submit pull requests on the GitHub repository. Please follow the code of conduct when contributing.

License

The @ddd-master/query-bus package is open-source software licensed under the MIT License.