Question

我不能创建一个扩展下面这个 DataRepository 类并访问其 JSON 文件中的键/值的类吗？

const fs = require("fs");

class DataRepository {
  constructor(filename) {
    if (!filename) {
      throw new Error("Creating a repository requires a filename");
    }

    this.filename = filename;
    try {
      fs.accessSync(this.filename);
    } catch (error) {
      console.error("data does not exist");
    }
  }

  async getAll() {
    // Open the file called this.filename
    return JSON.parse(
      await fs.promises.readFile(this.filename, {
        encoding: "utf-8",
      })
    );
  }

  async getOneBy(filters) {
    const records = await this.getAll();

    for (let record of records) {
      let found = true;

      for (let key in filters) {
        if (record[key] !== filters[key]) {
          found = false;
        }
      }

      if (found) {
        return record;
      }
    }
  }
}

module.exports = new DataRepository("cales_data.json");

当我遇到这个错误时，这是我正在尝试的：

const fs = require("fs");
const DataRepository = require("./repositories/data");

class Address extends DataRepository {
  constructor() {
    this.Address = DataRepository.Address;
    this.Latitude = DataRepository.Latitude;
    this.Longitude = DataRepository.Longitude;
  }
}

归根结底，我有一个 json 文件，它是一个对象数组，如下所示：

{
  'Number (original project order)': 99,
  FIELD2: null,
  Code_Notes: 'Not enough room to code historic preservation approval body',
  'Filler column to reference original sheet': '402 W Santa Clara St',
  City: 15,
  Planning_ID: 'PDC15-051',
  APN: '25938036',
  Total_Number_Parcels: -888,
  Address: '402 W Santa Clara St',
  Description_from_Agenda: 'A Planned Development Permit to allow the construction of a mixed use development with up to 1.04 million square feet for office/retail and up to 325 multi-family attached residences on a 8.93 gross acre site. ',
  Census_Tract: '5008.00',
  Council_District: '3',
  Neighborhood_Planning_Group: '-999',
  Community_Plan_Area: '-999',
  Specific_Plan_Area: 'Downtown',
  General_Plan_Designation: 'Downtown',

我希望能够通过 JavaScript 类访问其属性。

Answer 1

正如 georg 已经指出的，您需要导出类本身才能对其进行扩展。

module.exports = DataRepository;

由于您似乎想设置一个文件名，但无论如何该文件名在模块中都是硬编码的，所以您只需在构造函数中设置即可。

class DataRepository {
  constructor() {
    this.filename = "cales_data.json";
    try {
      fs.accessSync(this.filename);
    } catch (error) {
      console.error("data does not exist");
    }
  }
...

类型错误：类扩展值 #<DataRepository> 不是构造函数或 null

1 个答案: