使用打字稿在Firebase Cloud函数内部动态导入类的正确方法是什么? [英] What is the correct way to dynamically import a class inside of a Firebase Cloud function using typescript?

问题描述

在Firebase Cloud Function项目中...

我的src目录根目录中紧随主index.ts文件的旁边有以下打字稿文件，该文件导入一个依赖项并导出一个包含2个方法的类.该文件的标题为bcrypt.class.ts:

I have the following typescript file at the root of my src directory right along side of my main index.ts file which imports one dependency and exports a class that includes 2 methods. This file is titled bcrypt.class.ts:

import * as bcrypt from 'bcryptjs';

export default class BcryptTool {
  public static hashValue(value: string, rounds: number, callback: (error: Error, hash: string) => void) : void {
      bcrypt.hash(value, rounds, (error:any, hash:any) => {
            callback(error, hash);
      });
  }
  public static compare(value: string, dbHash: string, callback: (error: string | null, match: boolean | null) => void) {
    bcrypt.compare(value, dbHash, (err: Error, match: boolean) => {
        if(match) {
            callback(null, true);
        } else {
            callback('Invalid value match', null);
        }
    });
  }
}

在我的Firebase Cloud函数index.ts文件中，我导入该类并在我的一个函数中调用它的比较"方法而不会出现问题，这按预期工作:

In my Firebase Cloud functions index.ts file I import this class and make a call to it's 'compare' method within one of my functions without issue, this works as expected:

'use strict';
const express = require('express');
const functions = require('firebase-functions');
const cors = require('cors')({ origin: true });

const admin = require('firebase-admin');
admin.initializeApp();

const api = express();

import BcryptTool from './bcrypt.class'; // <-- i import the class here

// and use it in a function

api.use(cors);
api.post('/credentials', async (request: any, response: any) => {

   BcryptTool.compare(...) // <--- calls to this method succeed without issue

});

问题

我的应用程序包含许多函数，但是我只需要其中一个上面提到的类，因此，为了优化所有其他函数的冷启动时间，我尝试将此类动态导入到需要的函数中而不是将其导入到如上所述的全局范围中.这不起作用，我无法弄清楚原因:

My application includes many functions, but I only need the class noted above in one of them, so in an attempt to optimize cold start time for all my other functions, I attempt to dynamically import this class inside of the function that needs it instead of importing it into the global scope as outlined above. This does not work and I cannot figure out why:

'use strict';
const express = require('express');
const functions = require('firebase-functions');
const cors = require('cors')({ origin: true });

const admin = require('firebase-admin');
admin.initializeApp();

const api = express();

api.use(cors);
api.post('/credentials', async (request: any, response: any) => {

   const BcryptTool = await import('./bcrypt.class'); // <-- when i attempt to import here instead

   BcryptTool.compare(...) // <--- subsequent calls to this method fail

   // Additionally, VS Code hinting displays a warning: Property 'compare' does not exist on type 'typeof import('FULL/PATH/TO/MY/bcrypt.class')' 

});

我的班级写或输出错误吗?

Is my class not written or exported correctly?

我不是正确地在云函数内部导入了类吗?

Am I not importing the class correctly inside of my cloud function?

推荐答案

顶级导入(import BcryptTool from './bcrypt.class';)将自动从bcrypt.class模块导入default导出.但是，当将import语句用作函数(所谓的动态导入")时，它将导入模块本身，而不是默认导出.

The top-level import (import BcryptTool from './bcrypt.class';) will automatically import the default export from the bcrypt.class module. However, when using the import statement as a function (so called "dynamic import"), it will import the module itself, not the default export.

您将看到同时console.log(BcryptTool)两种导入的区别:

You can see the difference when you would console.log(BcryptTool) both imports:

• import BcryptTool from './bcrypt.class'将显示{ default: { [Function: BcryptTool] hashValue: [Function], compare: [Function] } }
• const BcryptTool = await require('bcrypt.class')将显示{ [Function: BcryptTool] hashValue: [Function], compare: [Function] }

• import BcryptTool from './bcrypt.class' will show { default: { [Function: BcryptTool] hashValue: [Function], compare: [Function] } }
• const BcryptTool = await require('bcrypt.class') will show { [Function: BcryptTool] hashValue: [Function], compare: [Function] }

您是否在第一个console.log中注意到default?这表明您导入了模块，而不是默认模块.

Did you notice the default in the first console.log? That shows you imported the module, not the default.

现在，import BcryptTool from './bcrypt.class'语法实际上是用于执行import { default as BcryptTool } from './bcrypt.class'的语法糖.如果您将此知识应用于动态导入，则可以执行以下操作:

Now actually the import BcryptTool from './bcrypt.class' syntax is syntactic sugar for doing import { default as BcryptTool } from './bcrypt.class'. If you apply this knowledge on the dynamic import, you could do this:

const BcryptToolModule = await import('./bcrypt.class');
BcryptToolModule.default.compare(...);

或者使用更简洁的语法:

Or in a cleaner syntax:

const { default: BcryptTool } = await import('./bcrypt.class');
BcryptTool.compare(...);

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