[VueJS + Typescript] Decouple Dependencies Using IoC Containers in Vue with TypeScript and InversifyJS

Using Object Oriented Programming, OOP, style allows us to apply Inversion of Control, IoC, and more patterns. An IoC container helps decoupling dependencies by using a class constructor or properties to identify and inject its dependencies. This lesson will show you how can you create and use an IoC container to decouple an http client and users service dependencies in a Vue component with TypeScript and InversifyJS.

When you are using Class, you also need to mantain the singleton of Class. Use can use similiar approach as Angular in VueJS as well.

Install:

npm i --save inversify reflect-metadata inversify-inject-decorators

Modify tsconfig.json:

{
  "compilerOptions": {
    "lib": [
      "dom",
      "es5",
      "es2015"
    ],
    "module": "es2015",
    "moduleResolution": "node",
    "target": "es5",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "allowSyntheticDefaultImports": true
  }
}

main.ts:

import "reflect-metadata"
import "core-js/es6/map"
import "core-js/es6/symbol"

import Vue from 'vue'
import App from './App.vue'

Vue.config.productionTip = false

/* eslint-disable no-new */
new Vue({
  el: '#app',
  template: '<App/>',
  components: { App }
})

Tip: If you want to create unqiue String, you can use Symbol('UserService'), it is useful tool.

Create a container.ts, which contains all the singleton services:

import {Container} from 'inversify';
import {UsersService} from './user-service';
import {HttpClient} from './http-client';
import {TYPES} from './types';
import getDecorators from 'inversify-inject-decorators';

const container = new Container();

container.bind<UserService>(TYPES.UsersService).to(UsersService);
container.bind<HttpClient>(TYPES.HttpClient).to(HttpClient);

// Lazy inject is good for props
const {lazyInject} = getDecorators(container);

export {container, lazyInject}

Create types.ts:

export const TYPES = {
    UsersService: Symbol('UsersService'),
    HttpClient: Symbol('HttpClient')
}

http-client.ts:

From:

export class HttpClient {
    get(url: string): Promise<any> {
        return fetch(url).then(data => data.json())
    }
}

To:

import {injectable} from 'inversify';

@injectable()
export class HttpClient {
    get(url: string): Promise<any> {
        return fetch(url).then(data => data.json())
    }
}

user-service.ts:

From:

export class UsersService {
    private http: HttpClient;

    constructor() {
        this.http = new HttpClient()
    }

    getUsers(): Promise<any> {
        return this.http.get('https://jsonplaceholder.type');
    }
}

To:

import {inject, injectable} from 'inversify';
import {TYPES} from './types';

@injectable()
export class UsersService {

    constructor(@inject(TYPES.HttpClient) private http) {
    }

    getUsers(): Promise<any> {
        return this.http.get('https://jsonplaceholder.type');
    }
}

Then we can use UsersService in App.vue:

<script lang="ts">
import Vue from 'vue'
import Component from 'vue-class-component'
import { lazyInject } from './container'
import { TYPES } from './types'
@Component
export default class App extends Vue {
  users = []
  @lazyInject(TYPES.UsersService)
  usersService
  created() {
    this.usersService.getUsers()
      .then(data => {
        this.users = data
      })
  }
}
</script>