Ensure that Vuex state is loaded before render component

问题

I have a add-user.vue component. It is my template for adding a new user and editing a existing user. So on page load I check if route has a id, if so I load a user from a state array to edit it. My issue is that user is undefined because the state array users is empty. How can I ensure that my user object isn't undefined. It does load sometimes but on refresh it doesn't. I thought I had it covered but nope. This is my setup. What am I missing here?

Store

state: {
  users: []
},

getters: {
  users: state =>
    _.keyBy(state.users.filter(user => user.deleted === false), 'id')
},

actions: {
  fetchUsers({
    commit
  }) {
    axios
      .get('http://localhost:3000/users')
      .then(response => {
        commit('setUsers', response.data);
      })
      .catch(error => {
        console.log('error:', error);
      });
  }
}

In my add-user.vue component I have the following in the data() computed:{} and created()

data() {
  return {
    user: {
      id: undefined,
      name: undefined,
      gender: undefined
    }
  };
},

computed: {
  ...mapGetters(['users'])
},

created() {
  if (this.$route.params.userId === undefined) {
    this.user.id = uuid();
    ...
  } else {
    this.user = this.users[this.$route.params.userId];
  }
}

Template

<template>
  <div class="add-user" v-if="user"></div>
</template>

My User.vue I have the following setup, where I init the fetch of users on created()

<template>
  <main class="main">
    <AddUser/>
    <UserList/>
  </main>
</template>

<script>
import AddUser from '@/components/add-user.vue';
import UserList from '@/components/user-list.vue';

export default {
    name: 'User',

    components: {
        AddUser,
        UserList
    },

    created() {
        this.$store.dispatch('fetchUsers');
    }
};
</script>

I have tried this. When saving in my editor it works but not on refresh. The dispatch().then() run before the mutation setting the users does.

created() {
  if (this.$route.params.userId === undefined) {
    this.user.id = uuid();
    ...
  } else {
    if (this.users.length > 0) {
                this.user = this.users[this.$route.params.userId];
            } else {
                this.$store.dispatch('fetchUsers').then(() => {
                    this.user = this.users[this.$route.params.userId];
                });
            }
  }
}

回答1:

I would use beforeRouteEnter in User.vue so that the component is not initialized before the data is loaded. (Assuming you are using vue-router)

beforeRouteEnter (to, from, next) {
    if (store.state.users.length === 0) {
        store.dispatch(fetchUsers)
        .then(next);
    }
},

You'll need to import store from 'path/to/your/store' because this.$store is not available until the component is initialized.

回答2:

For this particular case it was just going back and forth to the same vue instance. Solved it by adding :key="some-unique-key", so it looks like this.

<template>
  <main class="main">

    <AddUser :key="$route.params.userId"/>

    <UserList/>

  </main>
</template>

来源：https://stackoverflow.com/questions/51817967/ensure-that-vuex-state-is-loaded-before-render-component