How do I watch all keys in a data object in Vue 2

问题:

My data object:

data: {
    selected: {
        'type': null,
        'instrument': null
    },

My template:

<select v-model="selected['instrument']" @change="switchFilter('instrument', $event)">
    <option v-for="instrument in instruments" :value="instrument.value">@{{ instrument.text }}</option> 
</select>

<select v-model="selected['type']" @change="switchFilter('type', $event)">
    <option v-for="type in types" :value="type.value">@{{ type.text }}</option> 
</select>

How can I watch both selected indexes at the same time? I want to do something like this everytime any of the indexes updates:

watch: {
    selected: function(o, n) {
        ...
    }
}

回答1:

You can use deep option provided by the watcher from vue. As stated in the docs:

To also detect nested value changes inside Objects, you need to pass in deep: true in the options argument. Note that you don’t need to do so to listen for Array mutations.

You code will look like following:

watch: {
    'selected': {
        handler: function (val, oldVal) {
            console.log('watch 1', 'newval: ', val, '   oldVal:', oldVal)
        },
        deep: true
    }
}

回答2:

I think you can do this:

watch: {
    $data: {
        handler: function(val, oldVal) {
            console.log(val)
        },
        deep: true
    }
},

回答3:

watch: {
  'selected.type': function (newSelectedType) {
    console.log(newSelectedType)
  },

  'selected.instrument': function (newSelectedinstrument) {
    console.log(newSelectedinstrument)
  }
}

If you are just trying to calculate a new data from selected, you can just use computed properties, since the data of Vue are reactive, the computed properties can also detect the changes of data.

---

If you want to use a single function to watch the entire object, you can use $watch with deep: true:

mounted () {
  this.$watch('$data.selected', this.onSelectedUpdate, { deep: true })
}

note that '$data.selected' is a string, Vue will parse it.

and in your methods:

onSelectedUpdate (newSelected) {
  console.log(newSelected)
}