CODEWITHSUNDEEP
javascriptvue.jscomponents
isaac rivas
isaac rivas

Reputation: 21

Vue Watcher not working on component created with Vue.extend

I have a Parent component with a select input which is bound through v-model to a variable in data.

Besides, I create child components dynamically using Vue.extend, which i pass the propsData which also includes the value of the select.

This components have a watcher for the prop that is related to the select input.

When i create the component it receives the props succesfully, The problem comes when I update the value of the select input that doesn't trigger the watcher on the child component.

I've been looking for similar situations but have not found something that helps me solve this problem, i don't know why it doesn't trigger the watcher on the child component when the select input changes.

Any help would be very preciated.

Here i create the component dynamically:

let PresupuestoFormularioVue = Vue.extend(PresupuestoFormulario)
let instance = new PresupuestoFormularioVue({
  propsData: {
    //The prop related to select input  
    seguro: this.seguro,
  }
})
instance.$mount()
this.$refs.formularioContenedor.appendChild(instance.$el)

And this is the watcher in the component which isn't working:

watch:{
  seguro:{
    handler: function( newVal ){
      console.log(newVal)
    },
  },
},

Upvotes: 2

Views: 999

Answers (2)

mahdi-abaszadeh
mahdi-abaszadeh

Reputation: 21

All of props that you want check in watcher, should be a function. If you want read more about this go to vue document codegrepper.

watch: {
    // whenever seguro changes, this function will run
    seguro: function (newValue, oldValue) {
        console.log(newValue,oldValue)
    }
}

Upvotes: 2

tao
tao

Reputation: 90013

It's not the watch that doesn't work. It's the bindings. You're assigning the current value of this.seguro, not the reactive object itself. However, a new Vue() can add this binding for you.

As a sidenote, whether PresupuestoFormulario is a Vue.extend() doesn't matter. It can be any valid VueConstructor: a Vue.extend(), Vue.component() or a valid SFC (with name and template): export default {...}.

Here's how to do it:

methods: {
  addPresupuestoFormulario() {
    const div = document.createElement('div');
    this.$el.appendChild(div);
    new Vue({
      components: { PresupuestoFormulario },
      render: h => h("presupuesto-formulario", {
        props: {
          seguro: this.seguro
        }
      }) 
    }).$mount(div)
  }
}

The <div> initially appended to the parent will get replaced upon mounting with the actual template of PresupuestoFormulario and the bindings will be set, exactly as if you had <presupuesto-formulario :seguro="seguro" /> in the parent template from the start.

The really cool part about it is that the parent component doesn't need to have PresupuestoFormulario declared in its components.

Here's a working example:

const Test = Vue.component('test', {
  template: `<div>message: {{message}}</div>`,
  props: ['message'],
  watch: {
    message: console.log
  }
})

new Vue({
  el: '#app',
  data: () => ({
    msg: "¯\\_(ツ)_/¯"
  }),
  methods: {
    addComponent() {
      const div = document.createElement("div");
      this.$el.appendChild(div);
      new Vue({
        components: {
          Test
        },
        render: h => h("test", {
          props: {
            message: this.msg
          }
        })
      }).$mount(div);
    }
  }
})
<script src="https://cdn.jsdelivr.net/npm/vue@2"></script>
<div id="app">
  <input v-model="msg">
  <button @click="addComponent">Add dynamic child</button>
</div>

A separate note, about using this.$el.appendChild(). While this works when you're using a root Vue instance (a so-called Vue app), it will likely fail when using a normal Vue component, as Vue2 components are limited to having only 1 root element.
It's probably a good idea to have an empty container (e.g: <div ref="container" />) in the parent, and use this.$refs.container.appendChild() instead.

Upvotes: 2

Related Questions