Composition API implements Element-UI multi-level linkage. The main use of ref, reactive and computed to manage data, and functions to handle data changes to realize data-driven view updates. The key is to dynamically calculate the subordinate options based on the superior selection and reset the subordinate selection through the function to ensure the correctness of the linkage.

How to implement Element-UI multi-level linkage in Composition API?

You must have thought of using Composition API to implement multi-level linkage of Element-UI. This thing looks simple, but it is really useful and has a lot of tricks. We broke this article, crushed it, and said carefully. After reading it, you can not only handle multi-level linkage, but also have a deeper understanding of the Composition API and even make wheels by yourself!

Let’s talk about the conclusion first: using Composition API to achieve multi-level linkage of Element-UI, the core is to cleverly use ref , reactive and computed , as well as precise control of data changes. Don't be scared by those fancy codes. In fact, the principle is very simple, it is a data-driven view.

Let’s review the basics first. You must have used the Select component of Element-UI, right? It supports single choice itself, but multi-level linkage requires us to do it ourselves. Composition API is an important feature of Vue3. It allows us to organize our code in a more flexible way and improve the reusability and maintainability of our code. ref is used to create reactive references, reactive is used to create reactive objects, and computed is used to compute properties. These are our arsenal.

Now, let's directly upload the code, a simplified example, assuming your data structure is like this:

 <code class="javascript">const provinceData = [ { value: '1', label: '北京' }, { value: '2', label: '上海' }, { value: '3', label: '廣州' } ]; const cityData = { '1': [{ value: '11', label: '東城區(qū)' }, { value: '12', label: '西城區(qū)' }], '2': [{ value: '21', label: '黃浦區(qū)' }, { value: '22', label: '靜安區(qū)' }], '3': [{ value: '31', label: '越秀區(qū)' }, { value: '32', label: '海珠區(qū)' }] }; const districtData = { '11': [{ value: '111', label: '東華門' }], '12': [{ value: '121', label: '什剎海' }], // ... 省略其他區(qū)縣數(shù)據(jù)};</code>

Then, see how the Composition API works:

 <code class="javascript"><template> <el-select v-model="province"> <el-option v-for="item in provinceData" :key="item.value" :label="item.label" :value="item.value"></el-option> </el-select> <el-select v-model="city"> <el-option v-for="item in cityOptions" :key="item.value" :label="item.label" :value="item.value"></el-option> </el-select> <el-select v-model="district"> <el-option v-for="item in districtOptions" :key="item.value" :label="item.label" :value="item.value"></el-option> </el-select> </template> <script> import { ref, computed } from &#39;vue&#39;; export default { setup() { const province = ref(&#39;&#39;); const city = ref(&#39;&#39;); const district = ref(&#39;&#39;); const cityOptions = computed(() => { return cityData[province.value] || []; }); const districtOptions = computed(() => { return districtData[city.value] || []; }); const handleProvinceChange = () => { city.value = &#39;&#39;; // 級(jí)聯(lián)重置district.value = &#39;&#39;; // 級(jí)聯(lián)重置}; const handleCityChange = () => { district.value = &#39;&#39;; // 級(jí)聯(lián)重置}; return { province, city, district, cityOptions, districtOptions, handleProvinceChange, handleCityChange }; } }; </script></code>

The key to this code lies in the two computed properties of cityOptions and districtOptions . They dynamically calculate available city and district options based on the values ??of province and city . handleProvinceChange and handleCityChange functions are responsible for resetting the lower option when selecting the upper option to ensure the correctness of the linkage.

Remember, this is just a simplified example. In practical applications, you may need to process more data, more complex logic, and even consider the situation of asynchronous loading of data. But the core idea is the same: use ref , reactive and computed to manage data, use functions to handle data changes, and use data to drive view updates.

Finally, for performance optimization, you can consider using virtual lists or other optimization strategies, especially when your data volume is very large. The readability and maintainability of the code are also important, and try to keep the code concise and clear as much as possible. Don't forget to write comments, which will help you (and others) understand your code. Trust me, this will save you a lot of debugging time. Multi-level linkage may seem complicated, but as long as you master the core ideas, it is actually not difficult. come on!

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