前提

MacOS
VueCLI導入済み
Firebase導入・認証設定済み

本題

ログイン

src/store.js

//省略
//firebaseをインポート
import firebase from "firebase";

Vue.use(Vuex);

export default new Vuex.Store({
  state: {
    //追記
    login_user: null,
  },
  mutations: {
    //追記
    setLoginUser(state, user) {
      state.login_user = user;
    },
    addAddress(state, { id, address }) {
      address.id = id;
      state.addresses.push(address);
    },
    updateAddress(state, { id, address }) {
      const index = state.addresses.findIndex((address) => address.id === id);

      state.addresses[index] = address;
    },
    deleteAddress(state, { id }) {
      const index = state.addresses.findIndex((address) => address.id === id);

      state.addresses.splice(index, 1);
    },
  },
  actions: {
    //追記
    setLoginUser({ commit }, user) {
      commit("setLoginUser", user);
    },
    login() {
      const google_auth_provider = new firebase.auth.GoogleAuthProvider();
      firebase.auth().signInWithRedirect(google_auth_provider);
    },
    toggleSideMenu({ commit }) {
      commit("toggleSideMenu");
    },
    addAddress({ getters, commit }, address) {
      if (getters.uid) {
        firebase
          .firestore()
          .collection(`users/${getters.uid}/addresses`)
          .add(address)
          .then((doc) => {
            commit("addAddress", { id: doc.id, address });
          });
      }
    },
    updateAddress({ getters, commit }, { id, address }) {
      if (getters.uid) {
        firebase
          .firestore()
          .collection(`users/${getters.uid}/addresses`)
          .doc(id)
          .update(address)
          .then(() => {
            commit("updateAddress", { id, address });
          });
      }
    },
    deleteAddress({ getters, commit }, { id }) {
      if (getters.uid) {
        firebase
          .firestore()
          .collection(`users/${getters.uid}/addresses`)
          .doc(id)
          .delete()
          .then(() => {
            commit("deleteAddress", { id });
          });
      }
    },
  },
  modules: {},
  getters: {
    userName: (state) => (state.login_user ? state.login_user.displayName : ""),
    photoURL: (state) => (state.login_user ? state.login_user.photoURL : ""),
    uid: (state) => (state.login_user ? state.login_user.uid : null),
    getAddressById: (state) => (id) =>
      state.addresses.find((address) => address.id === id),
  },
});

続いて、ログインアクションを実行できるようにする。

views/home.vue

<template>
  <v-container text-center justify-center>
    <v-layout row wrap>
      <v-flex xs12>
        <h1>TEST</h1>
        <p>
          Googleアカウントでログイン
        </p>
      </v-flex>

      <v-flex xs12 mt-5>
        <v-btn color="info" @click="login">Googleアカウントでログイン</v-btn>
      </v-flex>
    </v-layout>
  </v-container>
</template>

<script>
//mapActionsを使用してmethodsに組み込む
import { mapActions } from "vuex";

export default {
  methods: {
    ...mapActions(["login"]),
  },
};
</script>

src/App.vue

<template>
  <v-app>
    <v-app-bar app color="primary" dark>
      <v-app-bar-nav-icon
        v-show="$store.state.login_user"
        @click.stop="toggleSideMenu"
      ></v-app-bar-nav-icon>
      <v-toolbar-title>TEST</v-toolbar-title>
      <v-spacer></v-spacer>
    </v-app-bar>
    <SideNav />

    <v-content>
      <v-container fluid fill-height align-start>
        <router-view />
      </v-container>
    </v-content>
  </v-app>
</template>

<script>
//追記
import firebase from "firebase";
import { mapActions } from "vuex";
//省略

export default {
  name: "App",

  components: {
    SideNav,
  },
  //追記
  created() {
    firebase.auth().onAuthStateChanged((user) => {
      if (user) {
        this.setLoginUser(user);
        this.fetchAddresses();
        if (this.$router.currentRoute.name === "home") {
          this.$router.push({ name: "addresses" }, () => {});
        }
      } else {
        this.deleteLoginUser();
        this.$router.push({ name: "home" }, () => {});
      }
    });
  },
  methods: {
    ...mapActions([
      "toggleSideMenu",
      "setLoginUser",
    ]),
  },
};
</script>

ログアウト

src/store.js

//省略

Vue.use(Vuex);

export default new Vuex.Store({
  state: {
    login_user: null,
  },
  mutations: {
    setLoginUser(state, user) {
      state.login_user = user;
    },
    //追記
    deleteLoginUser(state) {
      state.login_user = null;
    },
    addAddress(state, { id, address }) {
      address.id = id;
      state.addresses.push(address);
    },
    updateAddress(state, { id, address }) {
      const index = state.addresses.findIndex((address) => address.id === id);

      state.addresses[index] = address;
    },
    deleteAddress(state, { id }) {
      const index = state.addresses.findIndex((address) => address.id === id);

      state.addresses.splice(index, 1);
    },
  },
  actions: {
    setLoginUser({ commit }, user) {
      commit("setLoginUser", user);
    },
    login() {
      const google_auth_provider = new firebase.auth.GoogleAuthProvider();
      firebase.auth().signInWithRedirect(google_auth_provider);
    },
    //追記
    logout() {
      firebase.auth().signOut();
    },
    //追記
    deleteLoginUser({ commit }) {
      commit("deleteLoginUser");
    },
    toggleSideMenu({ commit }) {
      commit("toggleSideMenu");
    },
    addAddress({ getters, commit }, address) {
      if (getters.uid) {
        firebase
          .firestore()
          .collection(`users/${getters.uid}/addresses`)
          .add(address)
          .then((doc) => {
            commit("addAddress", { id: doc.id, address });
          });
      }
    },
    updateAddress({ getters, commit }, { id, address }) {
      if (getters.uid) {
        firebase
          .firestore()
          .collection(`users/${getters.uid}/addresses`)
          .doc(id)
          .update(address)
          .then(() => {
            commit("updateAddress", { id, address });
          });
      }
    },
    deleteAddress({ getters, commit }, { id }) {
      if (getters.uid) {
        firebase
          .firestore()
          .collection(`users/${getters.uid}/addresses`)
          .doc(id)
          .delete()
          .then(() => {
            commit("deleteAddress", { id });
          });
      }
    },
  },
  modules: {},
  getters: {
    userName: (state) => (state.login_user ? state.login_user.displayName : ""),
    photoURL: (state) => (state.login_user ? state.login_user.photoURL : ""),
    uid: (state) => (state.login_user ? state.login_user.uid : null),
    getAddressById: (state) => (id) =>
      state.addresses.find((address) => address.id === id),
  },
});

src/App.vue

<template>
  <v-app>
    <v-app-bar app color="primary" dark>
      <v-app-bar-nav-icon
        v-show="$store.state.login_user"
        @click.stop="toggleSideMenu"
      ></v-app-bar-nav-icon>
      <v-toolbar-title>TEST</v-toolbar-title>
      <v-spacer></v-spacer>
      //追記
      <v-toolbar-items v-if="$store.state.login_user">
        <v-btn text @click="logout">ログアウト</v-btn>
      </v-toolbar-items>
    </v-app-bar>
    <SideNav />

    <v-content>
      <v-container fluid fill-height align-start>
        <router-view />
      </v-container>
    </v-content>
  </v-app>
</template>

<script>
//追記
import firebase from "firebase";
import { mapActions } from "vuex";
//省略

export default {
  name: "App",

  components: {
    SideNav,
  },
  //追記
  created() {
    firebase.auth().onAuthStateChanged((user) => {
      if (user) {
        this.setLoginUser(user);
        this.fetchAddresses();
        if (this.$router.currentRoute.name === "home") {
          this.$router.push({ name: "addresses" }, () => {});
        }
      } else {
        this.deleteLoginUser();
        this.$router.push({ name: "home" }, () => {});
      }
    });
  },
  methods: {
    ...mapActions([
      "toggleSideMenu",
      "setLoginUser",
      //追記
      "logout",
      "deleteLoginUser",
      "fetchAddresses",
    ]),
  },
};
</script>