Vue 给mapState中定义的属性赋值报错的解决方案

1.   实践环境

Vue 2.9.6

2.   问题描述

<script>

import { mapState } from 'vuex';

export default {

    name: "displayCount",

    computed: {

        ...mapState({

            ...略

            count: state => state.a.count

        })

    },

    methods: {

        increaseCount () {

            this.count = this.count + 1

        }

    }

};

</script>

<style>

</style>

如上，我们希望在执行increaseCount函数时，给mapstate函数中映射定义的this.count赋值，给该值增加1，结果，提示

[Vue warn]: Computed property "count" was assigned to but it has no setter.

3.   解决方案1

如下，把属性“移出mapState”，然后为属性新增get，set方法，分别用于获取值和改变值（按store状态管理规定的方式）

<script>

import { mapState } from 'vuex';

export default {

    name: "displayCount",

    computed: {

        ...mapState({

...略

        }),

        count: {

            get() {

                return this.$store.state.a.count;

            },

            set(val) {

                this.$store.commit("increaseCount", val);

            }

        }

    },

    methods: {

        increaseCount () {

            this.count = this.count + 1

        }

    }

};

</script>

注意：this.$store.commit("increaseCount", val);中的increaseCount方法名称，并不是methods中定义的方法名称，而是store中定义的方法

4.   解决方案2

通过对比当前属性值和store状态值，然后根据比较结果，决定是否根据store状态管理规则更新状态值。

<script>

import { mapState } from 'vuex';

export default {

    name: "displayCount",

    computed: {

        ...mapState({

            count: state => state.a.count

        })

    },

    methods: {

        increaseCount () {

            if (this.count == this.$store.state.a.count) {

                this.$store.commit("increaseCount", this.count+1);

            }

        }

    }

};

</script>