Vuex rendering data that is fetched from REST API

One approach for asynchronously fetching data is to use promise in vuex store actions.

Vue.http.get(API_URL)
  .then((response) => {
     //use response object      
  })
  .catch((error) => {
    console.log(error.statusText)
  });

To demonstrate that I make request to this route. You can see how response should looks like. Let's save response object in state.users array.

store.js

const store = new Vuex.Store({
  state: {
    users: []
  },  
  mutations: {
    FETCH_USERS(state, users) {
      state.users = users
    }
  },
  actions: {
    fetchUsers({ commit }, { self }) {          
      Vue.http.get("https://jsonplaceholder.typicode.com/users")
        .then((response) => {
          commit("FETCH_USERS", response.body);
          self.filterUsers();   
        })
        .catch((error) => {
          console.log(error.statusText)
        });
    }
  }
})
    
export default store

You noticed that there is self.filteruser() method after commit. That is crucial moment. Before that we are committing a mutation, which is synchronous operation and we are sure that we will have our response in store.state that can be used in filterUsers() method (don't forget to pass self parm)

Users.vue

import store from "../store/store"

export default {
  name: 'users',
  created() {
    this.$store.dispatch("fetchUsers", { self: this })       
  },
  methods:{
    filterUsers() {
      //do something with users
      console.log("Users--->",this.$store.state.users)       
    }
  }
}

Better ways (ES6 & ES7)

ES6 Promises for asynchronous programming

//User.vue
created() {
  this.$store.dispatch("fetchUser").then(() => {
    console.log("This would be printed after dispatch!!")
  })
}

//store.js
actions: {
  fetchUser({ commit }) {
    return new Promise((resolve, reject) => {
      Vue.http.get("https://jsonplaceholder.typicode.com/users")
        .then((response) => {
          commit("FETCH_USERS", response.body);
          resolve();
         })
         .catch((error) => {
           console.log(error.statusText);
         });
    });
  }
}

ES7: async/await

To get away from callback hell, and to improve asynchronous programming use async function, and you can await on a promise. Code looks much easier to follow (like it is synchronous), but code isn't readable for browsers so you'll need Babel transpiler to run it.

actions: {
  async actionA ({ commit }) {
    commit('gotData', await getData())
  },
  async actionB ({ dispatch, commit }) {
    await dispatch('actionA') // wait for actionA to finish
    commit('gotOtherData', await getOtherData())
  }
}

In my experience, you can skip a few checks if you preset the state with an empty value of the same type as the expected result (if you know what to expect, of course), e.g. if you have an array of items, start with [] instead of null as it won't break v-for directives, .length checks and similar data access attempts.

But generally, adding v-if is a very normal thing to do. There's a section about this in the vue-router documentation and checking whether properties exist or not is exactly what it suggests. Another possible solution it mentions is fetching data inside beforeRouteEnter guard, which assures you will always get to the component with your data already available.

Ultimately, both solutions are correct, and the decision between them is more of a UX/UI question.