问Typescript泛型存储库模式-使用方法返回类型

EN

export class DynamoDbRepository<T extends IRepositoryItem> extends BaseRepository<T> {
    private _tableName: string = void 0;
    private _type;

    constructor(tableName: string, type: new () => T) {
    ...
    }

    ...

    findOne(appId: string, id: string): Promise<T> {
      const params = {
        Key: {
            "Id": id,
            "AppId": appId 
        },
        TableName: this._tableName
      }

      return new Promise((resolve, reject) => {
        DynamoDbClient.get(params, (error, result) => {
            // handle potential errors
            if (error) {
                Logger.error(error);
                reject(new Error(`GetItemFailed for table '${this._tableName}'`));
            }

            // no items found
            if (!result.Item) reject(new Error(`ItemNotFound in table '${this._tableName}'`));

            // create instance of correct type, map properties
            let item = new this._type();
            Object.keys(result.Item).forEach((key) => {
                item[key] = result.Item[key];
            })

            // return the item
            resolve(item);
        });
    });
}

const userRepository = new DynamoDbRepository<User>(Tables.USERS_TABLE, User);