Initialize Promises class fields in the constructor method

Question

I had done a test here with repositories, and this is the test:

export default class UserService {
    private userRepository: Repository<UserModel>;
    private connection: Connection;

    private async initialize(): Promise<any> {
        return createConnection()
        .then(v => this.connection = v)
        .then(_ => this.userRepository = this.connection.getRepository(UserModel))
      }

    constructor() {
    }

    public async findByUsername(username: string): Promise<UserModel> {
        let user: any;

        if(this.userRepository == undefined) {
            await this.initialize();
        }

        await this.userRepository.findOne({username: username}).then(v => user = v);
        return user;
    }

}

It's working, but the lint/TS Compiler is saying: the class fields userRepository and connection was not initialized in the constructor method.

All right, but this fields is of type Promise and the constructor is a sincronous method, so, how can I do the constructor initialize this fields?

Thanks

Answer 1

You can consider something like this:

export default class UserService {
  private connection: Promise<Connection> = createConnection();
  private userRepository: Promise<Repository<UserModel>> = this.connection.then(c =>
    c.getRepository(UserModel),
  );

  public async findByUsername(username: string): Promise<UserModel> {
    const userRepository = await this.userRepository;

    return await userRepository.findOne({ username });
  }
}