实例:

父组件:

app.component('父组件', {
  data() {
    return {
      todos: ['Feed a cat', 'Buy tickets']
    }
  },
  provide() {
    return {
      todoLength: this.todos.length
    }
  },
  template: `
    ...
  `
})

后代组件:

app.component('某一个隔了很多代的同系组件', {
  inject: ['todoLength'],
  created() {
    console.log(`Injected property: ${this.todoLength}`) // > 注入的 property: 2
  }
})