Vuex getter not updating value after an array update

Question

I'm trying to explore vuex, so what I'm trying to do is to get the count or an array when I remove or add values to it. Below are my codes.

home.vue template

<template>
    <div :class="page.class" :id="page.id">
        <h3>{{ content }}</h3>
        <hr>
        <p>Registered users count {{ unRegisteredUserCount }}</p>
        <ul class="list-unstyled" v-if="getUnRegisteredUsers">
            <li v-for="(unregistereduser, n) in getUnRegisteredUsers" @click="register(unregistereduser)">
                {{ n + 1 }}
                - {{ unregistereduser.id }} 
                {{ unregistereduser.fname }} 
                {{ unregistereduser.lname }}
            </li>
        </ul>
        <hr>
        <p>Registered users count {{ registeredUserCount }}</p>
        <ul class="list-unstyled">
            <li v-for="(registereduser, n) in getRegisteredUsers" @click="unregister(registereduser)">
                {{ n + 1 }}
                - {{ registereduser.id }} 
                {{ registereduser.fname }} 
                {{ registereduser.lname }}
            </li>
        </ul>
    </div>
</template>

<script>
    export default {
        name: 'home',
        data () {
            return {
                page: {
                    class: 'home',
                    id: 'home'
                },
                content: 'This is home page'
            }
        },
        computed: {
            getUnRegisteredUsers() {
                if( this.$store.getters.getCountUnregisteredUsers ) {
                    return this.$store.getters.getAllUnRegisteredUsers;
                }
            },
            getRegisteredUsers() {
                if( this.$store.getters.getCountRegisteredUsers > 0) {
                    return this.$store.getters.getAllRegisteredUsers;
                }
            },
            unRegisteredUserCount() {
                return  this.$store.getters.getCountUnregisteredUsers;
            },
            registeredUserCount() {
                return  this.$store.getters.getCountRegisteredUsers;
            }
        },
        methods: {
            register(unregistereduser) {
                this.$store.commit({
                    type: 'registerUser', 
                    userId: unregistereduser.id
                });
            },
            unregister(registereduser) {
                this.$store.commit({
                    type: 'unRegisterUser', 
                    userId: registereduser.id
                });
            }
        },
        mounted: function() {

        }
    }
</script>

state.js

export default {
    unRegisteredUsers: [
        {
            id: 1001,
            fname: 'John',
            lname: 'Doe',
            state: 'Los Angeles',
            registered: false
        },
        {
            id: 2001,
            fname: 'Miggs',
            lname: 'Ollesen',
            state: 'Oklahoma',
            registered: false
        },
        {
            id: 3001,
            fname: 'Zoe',
            lname: 'Mcaddo',
            state: 'New York',
            registered: false
        },
        {
            id: 4001,
            fname: 'Jane',
            lname: 'Roberts',
            state: 'Philadelphia',
            registered: false
        },
        {
            id: 5001,
            fname: 'Ellen',
            lname: 'Jennings',
            state: 'Houston',
            registered: false
        },
        {
            id: 6001,
            fname: 'Joseph',
            lname: 'Reed',
            state: 'Boston',
            registered: false
        },
        {
            id: 7001,
            fname: 'Jake',
            lname: 'Doe',
            state: 'Portland',
            registered: false
        }
    ],
    registeredUsers: []
}

getters.js

export default {
    getAllUnRegisteredUsers(state) {
        return state.unRegisteredUsers;
    },
    getAllRegisteredUsers(state) {
        return state.registeredUsers;
    },
    getCountUnregisteredUsers(state) {
        return state.unRegisteredUsers.length;
    },
    getCountRegisteredUsers(state) {
        return state.registeredUsers.length;
    },
    getUserById(state) {

    }
}

mutations.js

export default {
    registerUser(state, payload) {
        //find user
        const user = _.find(state.unRegisteredUsers, {
            'id': payload.userId
        });

        // remove user from original array
        _.remove(state.unRegisteredUsers, {
            'id': payload.userId
        });

        // set user object key value
        user.registered = 'true';

        // add user to new array
        state.registeredUsers.push(user);

        console.log(state.registeredUsers.length + ' - registered users count');
    },
    unRegisterUser(state, payload) {
        //find user
        const user = _.find(state.registeredUsers, {
            'id': payload.userId
        });

        // remove user from original array
        _.remove(state.registeredUsers, {
            'id': payload.userId
        });

        // set user object key value
        user.registered = 'false';

        // add user to new array
        state.unRegisteredUsers.push(user);

        console.log(state.unRegisteredUsers.length + ' - unregistered users count');
    }
}

During page load it renders the array count properly, but when I remove value to the registeredUsers and unRegisteredUsers the count is not updating. What am I missing here? Can anyone explain and what should I do to get the proper count? Thanks

Answer 1

The reason this is not working is that you are mutating an array. Never mutate an array. You'll spend hours trying to troubleshoot why reactivity broke.

Replace a value with a new array in order to retain reactivity. Use _.filter or _.reject, like the example below.

state.registeredUsers = _.reject(state.registeredUsers, {
    'id': payload.userId
});

The other answer by choasia is incorrect. Lodash is not the problem. Lodash is very helpful with Vuejs, you just need to use the functions that explicitly return a new array. See the Lodash docs under "returns" to know what it returns.