How to Two-way Data Binding Between Parents and grandchildren in Vue.js

Question

I faced a problem, I solve it by cookies but I want to solve the problem without cookies. I have a component which called app-header and It has another component which called outmodal. Now, My first Vue instance require component app-header.

var vue = new Vue({
    el : "html",
    data : {
        title       : "Site Title",
        description : "description of page",
        keywords    : "my keywords",
        view        : "home",
        login       : "login"
    },
    components:{
        "app-header" :require("../../components/header"),
        "app-footer" :require("../../components/footer"),
        "home"       :require("../../views/home")
    },
});

code of app-header

var Vue     = require("vue");

Vue.partial("login",require("../../partials/login.html"));
Vue.partial("logged",require("../../partials/logged.html"));

module.exports = {
    template    : require("./template.html"),
    replace     : true,
    components  : {
        outmodal : require("../outmodal")
    },
    props : ['login']
}

code of outmodal

var Vue = require("vue");
Vue.partial("loginModal",require("../../partials/loginModal.html"));

module.exports = {
    template    : require("./template.html"),
    replace     : true,
    props       : ['name'],
    data        : function () {
            return  {
                userLogin : { mail  :   "", password    :   "", remember    :   ""}
            }

    },
    methods : {
        formSubmit : function(e){
                e.preventDefault();
                this.$http.post("http://example.com/auth/login",{ "email": this.userLogin.mail , "password": this.userLogin.password },function(data,status,request){
                    $.cookie("site_token",data.token,{expires : 1})
                }).error(function(data,status,request){

                });

        }
    }, ready  : function(){
        console.log("it works")
    }
}

In outmodal component I connect the API and I check the login, If login will be succesfull, I want to change value of login variable in my Vue instance. I use web pack to build all requires. So I don't know how can I data binding between these files.

How can I solve It? I

Answer 1

The Best Solution which I found

For 0.12

http://012.vuejs.org/guide/components.html#Inheriting_Parent_Scope

for 1.0

http://v1.vuejs.org/guide/components.html#Parent-Child-Communication

for 2.0

https://vuejs.org/v2/guide/components.html#Composing-Components (use props to one-way bind data from parent to child)