如何从nestjs中的另一个文件导入变量？

Question

I try to import a variable from another file but i don't success. In my first file I have :

import { Injectable } from '@nestjs/common';

@Injectable()
export class Hello {
}
var varhello = "hi";

And in the other where i want to add varHello I have:

import { Injectable } from '@nestjs/common';
import * as hello from "./Hello";

@Injectable()
export class AppService {
  getHello(): any {
    console.log(hello.Hello)
  }
}

At least my console.log return something : [class Hello], but I want it to return the text "hi". Anyone know how to fix my problem?

Answer 1

Best practice would be to keep the greeting variable private inside hello class and have public methods for returning/modifying property that can be used by other classes, after that inject Hello service wherever you need it and call that method.

import { Injectable } from '@nestjs/common';

@Injectable()
export class Hello {
  private _greeting: string = 'Hi';

  get greeting(): string {
    return this._greeting;
  }
}

and then in your service:

import { Inject, Injectable } from '@nestjs/common';

import { Hello } from './Hello';

@Injectable()
export class AppService {
  @Inject()
  protected hello: Hello;

  getHello(): void {
    console.log(this.hello.greeting);
  }
}

Or if you want you could export a const variable like this

// Hello.ts file
export const hello = 'Hi';

And in your service you'll just import it

import { Injectable } from '@nestjs/common';

import { hello } from './Hello';

@Injectable()
export class AppService {
  getHello(): void {
    console.log(hello);
  }
}

But this way it will be just a const, and you won't be able to overwrite it.