为什么状态不会在计算中更新？

Question

I'm struggling for a couple of hours with vuex. It's the first time I use it and even though I follow the documentation something is not working but I really can't figure it out.

So I have the first example of the vuex doc that doesn't work. I have a count computed value that return the store state.

It's display on the page. The started value is 0 and the view is displaying 0. But hitting the buttons doesn't change the display.

If I put directly the store into the App.js in a constant, no problem it works.

I know I'm missing something...

homeStore.js

import Vue from 'vue'
import Vuex from 'vuex'

Vue.use(Vuex)

export default new Vuex.Store({
    state: {
        count: 0
    },
    mutations: {
        increment (state) {
            state.count++
        },
        decrement (state) {
            state.count--
        }
    }
})

App.js

import store from '../store/homeStore'

new Vue({
    el: '#app',
    store,
    computed: {
        count () {
            return store.state.count
        },
    },
    methods: {
        increment () {
            store.commit('increment')
        },
        decrement () {
            store.commit('decrement')
        }
    }
})

Answer 1

Make use of Vuex store actions

import Vue from 'vue'
import Vuex from 'vuex'
Vue.use(Vuex)
export default new Vuex.Store({
    state: { count: 0 },
    mutations: {
        increment (state) {
            state.count++ 
        },
       decrement (state) {
           state.count-- 
       }
    },
    actions: {
        increase ({ commit }) {
            commit('increment')
        },
        decrease ({ commit }) {
            commit('decrement')
        }
    }
 })

access the action method using this.$store.dispatch('increase') to increment the count and vice versa for decrement

Answer 2

If you try to console.log(store) , it will returns undefined .
The right way to access the store is to use this.$store (should be a component).

As mentioned in the doc:

By providing the store option to the root instance, the store will be injected into all child components of the root and will be available on them as this.$store .

Therefore, your updated code should be:

methods: {
    increment () {
        this.$store.commit('increment')
    },
    decrement () {
        this.$store.commit('decrement')
    }
}