javascript - 在构造方法中初始化 Promises 类字段

Question

我在这里用存储库做了一个测试，这是测试:

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;
    }

}

它正在工作，但 lint/TS 编译器说:类字段 userRepository 和连接未在构造方法中初始化。

好吧，但是这个字段是 Promise 类型，构造函数是一个 sincronous 方法，那么，我该如何让构造函数初始化这个字段？

谢谢

Answer 1

你可以这样考虑:

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 });
  }
}