Vuejs在v-model为空时隐藏一个div

Question

我有一个这样的选择下拉菜单。

<select v-model="selectedInjection">
    <option v-for="(match,i) in haufigkeitMatches"
        :key="i"
        :value="match.value" >{{ match.name }}
    </option>
</select>

我是这样渲染值的

<td v-if="selectedInjection">{{Math.round(selectedInjection)}</td>

{{Math.round(selectedInjection)} 的值会随着选择值的变化而变化，并且工作正常。但是当我没有选择任何值时，{{Math.round(selectedInjection)} 会显示旧的选择值，除非我选择一个新值。 选择值为空时如何隐藏{{Math.round(selectedInjection)}？

这是 Jsfiddle https://jsfiddle.net/ey3scra0/

Answer 1

最好在你的 div 中使用v-show：

<div class="hideResult" v-show="showSelectedInjection && selectedProduct != ''">
   {{Math.round(selectedInjection)}}
</div>

然后在第二次选择时添加@change：

<select v-model="selectedInjection" @change="setShowSelectedInjection">

您还需要使用方法setShowSelectedInjection 添加额外的字段showSelectedInjection 并在setSelectsToDefault 中设置showSelectedInjection：

data:{
showSelectedInjection: false,

(...)

methods:{
            setSelectsToDefault(){
                this.selectedIeProKg = 0;
                this.selectedPreisProIE = 0;
                this.showSelectedInjection = this.haufigkeitMatches.map(h => h.value).includes(this.selectedInjection);
            },
            setShowSelectedInjection(){
                this.showSelectedInjection = true;
            }

这是一个工作示例：JSFiddle

Answer 2

我不知道它对您的问题有多大影响，因为您没有提供应用程序中数据如何变化的示例。如果一个变量依赖于另一个变量，你必须观察它并控制它的变化。就像我这里一样，我跟随一个变量，检查它是否为空，然后重置第二个变量。如果还是不行，输入更多的数据，一段更大的代码，那我也会调整答案。

new Vue({
  data: {
    selectedInjection: null,
    haufigkeitMatches: []
  },
  computed: {
    round() {
      return Math.round(this.selectedInjection);
    }
  },
  watch: {
    haufigkeitMatches(val) {
      if (!val.length) {
        this.selectedInjection = null;
      }
    }
  },
  methods: {
    add() {
      this.haufigkeitMatches.push({
        name: 'Fus',
        value: 1.1
      }, {
        name: 'Ro',
        value: 2.2
      }, {
        name: 'Dah',
        value: 3.3
      })
    },
    del() {
      this.haufigkeitMatches = [];
    }
  }

}).$mount('#app');

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <select v-model="selectedInjection">
    <option v-for="(match,i) in haufigkeitMatches" :key="i" :value="match.value">{{ match.name }}</option>
  </select>
  <div v-show="selectedInjection">{{round}}</div>
  <div>DIV is {{selectedInjection ? 'visible' : 'invisible'}}</div>
  <button @click="add">Add</button>
  <button @click="del">Del</button>
</div>

Answer 3

这对我有用。每次都在清除旧值。请试试这个。

<div id="app">
                  <select v-model="selectedProduct" @change="setSelectsToDefault">
                    <option value=""></option>
                    <option v-for="(level1,index) in products"
                            :key="index"
                            :value="level1">{{level1.name}}</option>
                </select>
                <select v-model="selectedInjection">
                    <option v-for="(match,i) in haufigkeitMatches"
                            :key="i"
                            :value="match.value" >{{ match.name }}</option>
                </select>
                <table>
                  <tr>
                  <td class="table-result-body-ipJahr"><div class="hideResult" v-if="selectedInjection> 0">{{Math.round(selectedInjection)}}</div></td>
                </tr>
                </table>
</div>


    "use strict";

    new Vue({
        el: '#app',
        data: {
            selectedPreisProIE: [],
            selectedIeProKg: [],
            selectedGewicht: [],
            selectedInjection: '',
            selectedProduct: null,
            dataJson: [],
            products: [{
                name: "ivi",
                Hint: "45-60 IE/kg alle 5 Tage\n60 IE 1x/Woche\n30-40 IE 2 x/Woche",
                frequency: [1, 2, 8]
            }, {
                name: "ynovi",
                Hint: "40-50 IE/kg\n2x/Woche im Abstand\nvon 3-4 Tagen",
                frequency: [2, 6, 7]
            }, {
                name: "octa",
                Hint: "50 (25-65) IE/kg\nalle 3-5 Tage",
                frequency: [6, 7, 8]
            }, {
                name: "eroct",
                Hint: "50 IE/kg \nalle 4 Tage",
                frequency: [7]
            }, {
                name: "ltry",
                Hint: "20-40 I.E./kg\n2-3x/Woche",
                frequency: [2, 3]
            }, {
                name: "ate",
                Hint: "20-40 I.E./kg\nAlle 2-3 Tage",
                frequency: [5, 6]
            }, {
                name: "Facto A",
                Hint: "20-40 I.E./kg\nAlle 2-3 Tage",
                frequency: [5, 6]
            }, {
                name: "Eight",
                Hint: "40-60 I.E./kg \nJeden 3.Tag oder\n2x/Woche",
                frequency: [2, 3, 5, 6]
            }, {
                name: "iq_Vima",
                Hint: "20-40 I.E./kg\nAlle 2-3 Tage",
                frequency: [5, 6]
            }, {
                name: "Afla",
                Hint: "20-50 I.E./kg\n2-3x/Woche",
                frequency: [2, 3]
            }, {
                name: "Pma",
                Hint: "20-40 I.E./kg\nAlle 2-3 Tage",
                frequency: [5, 6]
            }, {
                name: "others",
                Hint: "Individuell",
                frequency: [1, 2, 3, 4, 5, 6, 7, 8]
            }],
            haufigkeit: [{
                name: "1x / Woche",
                id: 1,
                value: 52.1428571429
            }, {
                name: "2x / Woche",
                value: 104.2857142857143,
                id: 2
            }, {
                name: "3x / Woche",
                value: 156.4285714285714,
                id: 3
            }, {
                name: "alle 1 Tage",
                value: 365,
                id: 4
            }, {
                name: "alle 2 Tage",
                value: 182.5,
                id: 5
            }, {
                name: "alle 3 Tage",
                value: 121.6666666666667,
                id: 6
            }, {
                name: "alle 4 Tage",
                value: 91.25,
                id: 7
            }, {
                name: "alle 5 Tage",
                value: 73,
                id: 8
            }]
        },
        computed: {
            haufigkeitMatches: function haufigkeitMatches() {
                var _this = this;

                if (this.selectedProduct) {
                    return this.haufigkeit.filter(function (x) {
                        return _this.selectedProduct.frequency.includes(x.id);
                    });
                }
            },
        },
        methods:{
            setSelectsToDefault(){
                this.selectedIeProKg = 0;
                this.selectedPreisProIE = 0;
                this.selectedGewicht = 0;
                this.selectedInjection='';
            }
            }
    });