vuejs2 passing data between parent-child is wiping childs value - vue.js

Question

In VueJS 2 I am trying to create a component that gets and passes data back to the parent which then passes it to another component to display.
The component that gets the data has a user input field it uses to search. When I have it pass data back to the parent using $emit the value in the input keeps being wiped.
I am receiving the below mutation error but I haven't directly tried to change the userSearch field in the component so I am not sure why.
"Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop's value. Prop being mutated: "userSearch" (found in PersonField)"
Relevant html
<person-field v-on:event_child="eventChild"></person-field>
<person-search :prop="personListArray" ></person-search>
Parent app
var app = new Vue({
el: '#app',
data: {
personListArray : [],
tempArray: []
},
methods: {
eventChild: function (arr) {
this.personListArray = arr
}
}
})
Component 1, displays a user input. Uses the input to search and bring back data. Starts search when the length of the input is more then 2. As soon as you hit the 3rd character something is causing the input to clear which I don't want.
Vue.component('person-field', {
props: ['userSearch'],
template: '<input class="form-control" v-model="userSearch" >',
watch: {
userSearch: function () {
var arr = []
if (typeof this.userSearch !== 'undefined') { //added this because once i passed 3 characters in the field the userSearch variable becomes undefined
if (this.userSearch.length > 2) {
$.each(this.getUsers(this.userSearch), function (index, value) {
var obj = {
Title: value.Title,
ID: value.ID
}
arr.push(obj)
});
this.$emit('event_child', arr) //emits the array back to parent "eventChild" method
} else {
console.log('no length')
}
} else {
console.log('cant find field')
}
},
},
methods: {
getUsers: function (filter) {
//gets and returns an array using the filter as a search
return arr
},
}
});
Component 2 - based on the personListArray which is passed as a prop, displays the results as a list (this works)
Vue.component('person-search', {
props: ['prop'],
template: '<ul id="personList">' +
'<personli :ID="person.ID" v-for="person in persons">' +
'<a class="" href="#" v-on:click="fieldManagerTest(person.Title, person.ID)">{{person.Title}}</a>' +
'</personli></ul>',
computed: {
persons: function () {
return this.prop
}
},
methods: {
fieldManagerTest: function (title, ID) { //Remove item from users cart triggered via click of remove item button
//var user = ID + ';#' + title
//this.internalValue = true
//this.$emit('fieldManagerTest');
//this.$parent.$options.methods.selectManager(user)
},
},
});
Component 3, part of component 2
Vue.component('personli', {
props: ['ID'],
template: '<transition name="fade"><li class="moving-item" id="ID"><slot></slot></li></transition>'
})
;

Answer 1

The reason you get the warning,
Avoid mutating a prop directly since the value will be overwritten
whenever the parent component re-renders. Instead, use a data or
computed property based on the prop's value. Prop being mutated:
"userSearch" (found in PersonField)
Is because of this line
<input class="form-control" v-model="userSearch" >
v-model will attempt to change the value of the expression you've told it to, which in this case is userSearch, which is a property.
Instead, you might copy userSearch into a local variable.
Vue.component('person-field', {
props: ['userSearch'],
data(){
return {
searchValue: this.userSearch
}
},
template: '<input class="form-control" v-model="searchValue" >',
...
})
And modify your watch to use searchValue.
Here is an example.