Vue component development: multi-level linkage selector implementation

Vue component development: multi-level linkage selector implementation

In front-end development, multi-level linkage selector is a common requirement, such as province and city selection, Year, month, day selection, etc. This article will introduce how to use Vue components to implement multi-level linkage selectors, with specific code implementation examples.

How to implement multi-level linkage selector?

To implement multi-level linkage selectors, you need to use Vue's component development idea to split a large selector into several sub-components, which are responsible for rendering each level of options. Each time the level selection changes, the options of subsequent levels must be updated, which requires the use of a communication mechanism between Vue components.

In addition, the selector needs to receive the initial value from the outside and send event notifications to the outside when the selection changes. This can be achieved using props and $emit.

Let’s gradually implement this multi-level linkage selector component.

Step 1: Define subcomponents

We first define the selector subcomponent for each level. The following is the code for a simple subcomponent of the province selector:

<template>
  <select v-model="selected">
    <option value="">请选择</option>
    <option v-for="item in options" :value="item">{{ item }}</option>
  </select>
</template>

<script>
export default {
  props: {
    options: {
      type: Array,
      required: true
    },
    value: {
      type: String,
      default: ''
    }
  },
  data() {
    return {
      selected: this.value
    }
  },
  watch: {
    selected(newValue) {
      this.$emit('change', newValue)
    }
  }
}
</script>

Code explanation:

• Use the select tag to render the drop-down option box, and use v-model to bind the current option The value of , and initialize the selected value through data();
• Use watch to monitor changes in the selected value, send a change event when the option changes, and notify the parent component of the new selected value.
Step 2: Define the parent component
Next, we define the parent component of the multi-level linkage selector. This component is responsible for rendering all child components and updating the options of subsequent child components when the options change.

The following is the code for a simple two-level linkage selector:

<template>
  <div>
    <CitySelect :options="provinces" v-model="selectedProvince"/>
    <CitySelect :options="cities" v-model="selectedCity"/>
  </div>
</template>

<script>
import CitySelect from './CitySelect.vue'

export default {
  components: {
    CitySelect
  },
  data() {
    return {
      provinces: ['广东', '江苏', '浙江'],
      cities: {
        '广东': ['广州', '深圳'],
        '江苏': ['南京', '苏州'],
        '浙江': ['杭州', '宁波']
      },
      selectedProvince: '',
      selectedCity: ''
    }
  },
  watch: {
    selectedProvince(newValue) {
      this.selectedCity = ''
      if (newValue) {
        this.cities = this.$data.cities[newValue]
      } else {
        this.cities = []
      }
    }
  }
}
</script>

Code explanation:

Use two CitySelect subcomponents in the template and render them separately. The province and city selection boxes bind the currently selected provinces and cities through v-model;

Define two arrays, provinces and cities, in the data function. The provinces array stores all provinces, and the cities object stores all Cities, use selectedProvince and selectedCity to record the currently selected provinces and cities;

• Monitor changes in selectedProvince in the watch, and update the cities array when the province changes, which is used to render the next-level city selection box.
Step 3: Combine all sub-components
After we have defined all sub-components and parent components, we only need to combine all sub-components to form a complete The multi-level linkage selector.

The following is the code for a simple three-level linkage selector:

<template>
  <div>
    <RegionSelect :options="provinces" v-model="selectedProvince"/>
    <RegionSelect :options="cities" v-model="selectedCity"/>
    <RegionSelect :options="districts" v-model="selectedDistrict"/>
  </div>
</template>

<script>
import RegionSelect from './RegionSelect.vue'

export default {
  components: {
    RegionSelect
  },
  data() {
    return {
      provinces: ['广东', '江苏', '浙江'],
      cities: {
        '广东': ['广州', '深圳'],
        '江苏': ['南京', '苏州'],
        '浙江': ['杭州', '宁波']
      },
      districts: {
        '广州': ['天河区', '海珠区'],
        '深圳': ['福田区', '南山区'],
        '南京': ['玄武区', '鼓楼区'],
        '苏州': ['姑苏区', '相城区'],
        '杭州': ['上城区', '下城区'],
        '宁波': ['江东区', '江北区']
      },
      selectedProvince: '',
      selectedCity: '',
      selectedDistrict: ''
    }
  },
  watch: {
    selectedProvince(newValue) {
      if (newValue) {
        this.cities = this.$data.cities[newValue]
        this.selectedCity = ''
        this.districts = []
      } else {
        this.cities = []
        this.districts = []
      }
    },
    selectedCity(newValue) {
      if (newValue) {
        this.districts = this.$data.districts[newValue]
        this.selectedDistrict = ''
      } else {
        this.districts = []
      }
    }
  }
}
</script>

Code explanation:

Use three RegionSelect subcomponents in the template and render them separately. The selection boxes for provinces, cities and districts are bound to the currently selected provinces, cities and districts through v-model;

Define three objects provinces, cities and districts in the data function, and the provinces array stores all provinces , the cities object stores all cities, and the districts object stores all districts. Use selectedProvince, selectedCity and selectedDistrict to record the currently selected province, city and district;

• Monitor the changes of selectedProvince and selectedCity in the watch. When the province or When the city changes, the options and selected values ​​of subsequent selection boxes are updated.
The three-level linkage selector has been completed! You can reference the component in the Vue component template, as shown below:

• <template>
    <div>
      <RegionSelect v-model="selectedRegion"/>
    </div>
  </template>
  
  <script>
  import RegionSelect from './RegionSelect.vue'
  
  export default {
    components: {
      RegionSelect
    },
    data() {
      return {
        selectedRegion: ['广东', '深圳', '南山区']
      }
    }
  }
  </script>

  Summary

  This article introduces how to use Vue components to implement multi-level linkage selectors, including defining child components and parent components , and the process of combining all subcomponents. Through this example, we can understand the basic ideas of Vue component development and the communication mechanism between components. Of course, more details need to be considered in actual development, such as asynchronous data acquisition, modifying the style of the subcomponent itself, etc. These contents are not covered in this article.

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