How to use Provide/Inject in Vue.js with TypeScrip

Question

I'm using Vue.js with TypeScript and the vue-property-decorator package. In theory I can do something like this, according to the documentation:

import { Component, Inject, Provide, Vue } from 'vue-property-decorator'

const s = Symbol('baz')

@Component
export class MyComponent extends Vue {
  @Provide() foo = 'foo'
  @Provide('bar') baz = 'bar'

  @Inject() foo: string
  @Inject('bar') bar: string
  @Inject(s) baz: string
}

However, what if I want to use @Provide and @Inject on a class that is not a component? For example, if I have ComponentA that depends on ServiceA that depends on ServiceB. How can i set this up?

Answer 1

You provide anything you want from a higher component by using the @Provide decorator and then ask for it in a lower component by using @Inject. For example:

In the parent component you provide the value using @Provide(<someKey>)

//Parent.vue
<template>
  <div>The parents value: {{this.providedValue}}</div>
  <child />
</template>

<script lang="ts">
  import { Component, Vue, Provide} from 'vue-property-decorator';
  import Child from './Child.vue';

  @Component({components: Child})
  export default class Parent extends Vue {
    @Provide('key') private providedValue: string = 'The value';
  }
</script>

Now we've declared a value with the name key that can be consumed by all children, multiple levels deep:

//Child.vue
<template>
  <div>The childs value: {{this.injectedValue}}</div>
</template>

<script lang="ts>
  import { Component, Vue, Inject } from 'vue-property-decorator';

  @Component
  export default class Child extends Vue {
    @Inject('key') private injectedValue!: string;
  }
</script>

The property injectedValue will now be injected by Vue by walking up on the hierarchy until it finds a provided value with the key key.

---

If you want something dependency injection-like, it's best to provide the value at the top, where you create your Vue instance:

//index.ts
import Vue from 'vue';
//... imports and configs
new Vue({
  el: '#app',
  // Provide values by returning a key-value pair
  provide: () => ({
    'key1': 'value1',
    'key2': 'value2'
  }),
  render: h => h(App)
});

Now you can use @Inject('key1') in any component of this vue instance.