Vuex Action vs Mutations

Question

In Vuex, what is the logic of having both \"actions\" and \"mutations?\"

I understand the logic of components not being able to modify state (which seems smart), but

Answer 1

This confused me too so I made a simple demo.

component.vue

<template>
    <div id="app">
        <h6>Logging with Action vs Mutation</h6>
        <p>{{count}}</p>
        <p>
            <button @click="mutateCountWithAsyncDelay()">Mutate Count directly with delay</button>
        </p>
        <p>
            <button @click="updateCountViaAsyncAction()">Update Count via action, but with delay</button>
        </p>
        <p>Note that when the mutation handles the asynchronous action, the "log" in console is broken.</p>
        <p>When mutations are separated to only update data while the action handles the asynchronous business
            logic, the log works the log works</p>
    </div>
</template>

<script>

        export default {
                name: 'app',

                methods: {

                        //WRONG
                        mutateCountWithAsyncDelay(){
                                this.$store.commit('mutateCountWithAsyncDelay');
                        },

                        //RIGHT
                        updateCountViaAsyncAction(){
                                this.$store.dispatch('updateCountAsync')
                        }
                },

                computed: {
                        count: function(){
                                return this.$store.state.count;
                        },
                }

        }
</script>

store.js

import 'es6-promise/auto'
import Vuex from 'vuex'
import Vue from 'vue';

Vue.use(Vuex);

const myStore = new Vuex.Store({
    state: {
        count: 0,
    },
    mutations: {

        //The WRONG way
        mutateCountWithAsyncDelay (state) {
            var log1;
            var log2;

            //Capture Before Value
            log1 = state.count;

            //Simulate delay from a fetch or something
            setTimeout(() => {
                state.count++
            }, 1000);

            //Capture After Value
            log2 = state.count;

            //Async in mutation screws up the log
            console.log(`Starting Count: ${log1}`); //NRHG
            console.log(`Ending Count: ${log2}`); //NRHG
        },

        //The RIGHT way
        mutateCount (state) {
            var log1;
            var log2;

            //Capture Before Value
            log1 = state.count;

            //Mutation does nothing but update data
            state.count++;

            //Capture After Value
            log2 = state.count;

            //Changes logged correctly
            console.log(`Starting Count: ${log1}`); //NRHG
            console.log(`Ending Count: ${log2}`); //NRHG
        }
    },

    actions: {

        //This action performs its async work then commits the RIGHT mutation
        updateCountAsync(context){
            setTimeout(() => {
                context.commit('mutateCount');
            }, 1000);
        }
    },
});

export default myStore;

After researching this, the conclusion I came to is that mutations are a convention focused only on changing data to better separate concerns and improve logging before and after the updated data. Whereas actions are a layer of abstraction that handles the higher level logic and then calls the mutations appropriately