我同时使用vuex和vuejs 2。
我是vuex的新手，我想看一个商店变量的变化。
我想在我的vue组件中添加手表功能
这是我目前所拥有的:
import Vue from 'vue';
import {
MY_STATE,
} from './../../mutation-types';
export default {
[MY_STATE](state, token) {
state.my_state = token;
},
};
我想知道my_state是否有任何变化
我怎么看店。My_state在我的vuejs组件?
当前回答
比如说，你有一篮水果， 每次你从篮子里添加或取出一个水果，你 想要(1)显示有关水果数量的信息，但你也(2)想要以某种奇特的方式通知水果的数量…
fruit-count-component.vue
<template>
<!-- We meet our first objective (1) by simply -->
<!-- binding to the count property. -->
<p>Fruits: {{ count }}</p>
</template>
<script>
import basket from '../resources/fruit-basket'
export default () {
computed: {
count () {
return basket.state.fruits.length
// Or return basket.getters.fruitsCount
// (depends on your design decisions).
}
},
watch: {
count (newCount, oldCount) {
// Our fancy notification (2).
console.log(`We have ${newCount} fruits now, yay!`)
}
}
}
</script>
请注意，监视对象中的函数名必须与计算对象中的函数名匹配。在上面的例子中，名字是count。
被监视属性的新值和旧值将作为参数传递到监视回调(count函数)。
篮子商店可以是这样的:
fruit-basket.js
import Vue from 'vue'
import Vuex from 'vuex'
Vue.use(Vuex)
const basket = new Vuex.Store({
state: {
fruits: []
},
getters: {
fruitsCount (state) {
return state.fruits.length
}
}
// Obviously you would need some mutations and actions,
// but to make example cleaner I'll skip this part.
})
export default basket
你可以在以下资源中阅读更多:
计算属性和监视器 API文档:计算 API文档:观察
其他回答
比如说，你有一篮水果， 每次你从篮子里添加或取出一个水果，你 想要(1)显示有关水果数量的信息，但你也(2)想要以某种奇特的方式通知水果的数量…
fruit-count-component.vue
<template>
<!-- We meet our first objective (1) by simply -->
<!-- binding to the count property. -->
<p>Fruits: {{ count }}</p>
</template>
<script>
import basket from '../resources/fruit-basket'
export default () {
computed: {
count () {
return basket.state.fruits.length
// Or return basket.getters.fruitsCount
// (depends on your design decisions).
}
},
watch: {
count (newCount, oldCount) {
// Our fancy notification (2).
console.log(`We have ${newCount} fruits now, yay!`)
}
}
}
</script>
请注意，监视对象中的函数名必须与计算对象中的函数名匹配。在上面的例子中，名字是count。
被监视属性的新值和旧值将作为参数传递到监视回调(count函数)。
篮子商店可以是这样的:
fruit-basket.js
import Vue from 'vue'
import Vuex from 'vuex'
Vue.use(Vuex)
const basket = new Vuex.Store({
state: {
fruits: []
},
getters: {
fruitsCount (state) {
return state.fruits.length
}
}
// Obviously you would need some mutations and actions,
// but to make example cleaner I'll skip this part.
})
export default basket
你可以在以下资源中阅读更多:
计算属性和监视器 API文档:计算 API文档:观察
正如Gabriel所说，观察商店变化的最佳方法是使用mapGetters。 但在某些情况下，你不能通过mapGetters来实现，例如，你想从store中获取一些东西，使用parameter:
getters: {
getTodoById: (state, getters) => (id) => {
return state.todos.find(todo => todo.id === id)
}
}
在这种情况下，你不能使用mapGetters。你可以试着这样做:
computed: {
todoById() {
return this.$store.getters.getTodoById(this.id)
}
}
但不幸的是，todoById仅在以下情况下才会更新。Id改变了
如果你想更新你的组件在这种情况下使用。$store。腕表解决方案由龚提供。或者有意识地处理组件并更新它。当需要更新todoById时，使用todoById。
我想尽了一切办法让它运转起来。
理论
我发现，出于某种原因，对$store对象的更改不一定会触发.watch方法。我的解决办法是
Store Create a complex data set which should but doesn't propagate changes to a Component Create an incrementing counter in the state to act as a flag, which does propagate changes to a Component when watched Create a method in $store.mutators to alter the complex dataset and increment the counter flag Component Watch for changes in the $store.state flag. When change is detected, update locally relevant reactive changes from the $store.state complex data set Make changes to the $store.state's dataset using our $store.mutators method
实现
它的实现是这样的:
商店
let store = Vuex.Store({
state: {
counter: 0,
data: { someKey: 0 }
},
mutations: {
updateSomeKey(state, value) {
update the state.data.someKey = value;
state.counter++;
}
}
});
组件
data: {
dataFromStoreDataSomeKey: null,
someLocalValue: 1
},
watch: {
'$store.state.counter': {
immediate: true,
handler() {
// update locally relevant data
this.someLocalValue = this.$store.state.data.someKey;
}
}
},
methods: {
updateSomeKeyInStore() {
this.$store.commit('updateSomeKey', someLocalValue);
}
可运行演示
这很复杂，但基本上我们在这里观察一个要更改的标志，然后更新本地数据以反映存储在$状态中的对象的重要更改
Vue.config.devtools = false const store = new Vuex.Store({ state: { voteCounter: 0, // changes to objectData trigger a watch when keys are added, // but not when values are modified? votes: { 'people': 0, 'companies': 0, 'total': 0, }, }, mutations: { vote(state, position) { state.votes[position]++; state.voteCounter++; } }, }); app = new Vue({ el: '#app', store: store, data: { votesForPeople: null, votesForCompanies: null, pendingVote: null, }, computed: { totalVotes() { return this.votesForPeople + this.votesForCompanies }, peoplePercent() { if (this.totalVotes > 0) { return 100 * this.votesForPeople / this.totalVotes } else { return 0 } }, companiesPercent() { if (this.totalVotes > 0) { return 100 * this.votesForCompanies / this.totalVotes } else { return 0 } }, }, watch: { '$store.state.voteCounter': { immediate: true, handler() { // clone relevant data locally this.votesForPeople = this.$store.state.votes.people this.votesForCompanies = this.$store.state.votes.companies } } }, methods: { vote(event) { if (this.pendingVote) { this.$store.commit('vote', this.pendingVote) } } } }) <script src="https://cdn.jsdelivr.net/npm/vue@2.6.12"></script> <script src="https://unpkg.com/vuex@3.5.1/dist/vuex.js"></script> <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/css/bootstrap.min.css"> <div id="app"> <form @submit.prevent="vote($event)"> <div class="form-check"> <input class="form-check-input" type="radio" name="vote" id="voteCorps" value="companies" v-model="pendingVote" > <label class="form-check-label" for="voteCorps"> Equal rights for companies </label> </div> <div class="form-check"> <input class="form-check-input" type="radio" name="vote" id="votePeople" value="people" v-model="pendingVote" > <label class="form-check-label" for="votePeople"> Equal rights for people </label> </div> <button class="btn btn-primary" :disabled="pendingVote==null" >Vote</button> </form> <div class="progress mt-2" v-if="totalVotes > 0" > <div class="progress-bar" role="progressbar" aria-valuemin="0" :style="'width: ' + peoplePercent + '%'" :aria-aluenow="votesForPeople" :aria-valuemax="totalVotes" >People</div> <div class="progress-bar bg-success" role="progressbar" aria-valuemin="0" :style="'width: ' + companiesPercent + '%'" :aria-valuenow="votesForCompanies" :aria-valuemax="totalVotes" >Companies</div> </div> </div>
你也可以订阅商店突变:
store.subscribe((mutation, state) => {
console.log(mutation.type)
console.log(mutation.payload)
})
https://vuex.vuejs.org/api/#subscribe
在computed中使用你的getter，然后观察它并做你需要做的事情
computed:{
...mapGetters(["yourGetterName"])
},
watch: {
yourGetterName(value) {
// Do something you need
},
}
