The main problems with the Vue and Element-UI cascaded drop-down boxes are caused by data structure errors, improper asynchronous loading and value update issues. First, the cascading selector requires a tree-like data structure, the data contains label and children attributes. Secondly, when loading data asynchronously, you must use Promise and use functions on the options attribute. Finally, double check the correctness of v-model binding and @change event handling.

Vue and Element-UI Cascaded Pull-down Box FAQ: Those pitfalls and stories you have to tell

Many friends use cascading selectors when building projects with Vue and Element-UI. This thing looks simple, but it often makes people crazy when used. In this article, let’s talk about the pitfalls that make people feel troubled and how to avoid them gracefully. After reading, you can not only solve the problems in front of you, but also improve your understanding of Vue components and data flows, and even write more elegant and robust code.

First of all, it must be clear that the cascade selector of Element-UI itself is a powerful component, and the problem is mostly how we use it. Many times, we simply attribute the problem to the bugs in the component itself, but it is not.

Basic knowledge, go through it first

Let’s first review the core idea of ??Vue: data-driven views. Element-UI's cascade selector, which is essentially a Vue component, which receives data through props and affects data through event callbacks. Once you understand this, many problems can be solved easily. In addition, you have to be familiar with the Element-UI's cascade selector API documentation, which is your treasure.

The core of the cascade selector: data structure

The core of the cascading selector is the data structure. It relies on a tree-like data, usually an array, each item of the array represents a node, each node contains label (display text) and children (child nodes) properties. The data structure is wrong and everything is messed up. For example, if your data structure is not standardized, or the data is loaded asynchronously, various strange problems will arise, such as incorrect display of options, the selected value cannot be updated, etc.

Code examples, practical drills

Suppose we have a three-level linkage, provinces, cities and districts, and the data structure is as follows:

 <code class="javascript">const provinces = [ { label: '廣東', value: 'gd', children: [ { label: '廣州', value: 'gz', children: [{ label: '天河', value: 'th' }] }, { label: '深圳', value: 'sz', children: [{ label: '南山', value: 'ns' }] } ] }, { label: '北京', value: 'bj', children: [ { label: '朝陽', value: 'cy' }, { label: '海淀', value: 'hd' } ] } ];</code>

In the component, use this:

 <code class="vue"><template> <el-cascader v-model="selectedOptions" :options="provinces"></el-cascader> </template> <script> export default { data() { return { selectedOptions: [], // 選中值provinces: provinces // 省市區(qū)數(shù)據(jù)}; }, methods: { handleChange(value) { console.log(value); // 處理選中值} } }; </script></code>

Advanced usage, advanced skills

If your data is loaded asynchronously, you need to use a function on options property, which returns a Promise, and then returns the data after the Promise resolves. Remember to handle the loading status well and avoid bad user experience.

Common errors and debugging methods

• Data structure error: Carefully check whether your data structure meets the requirements of Element-UI, you can use console.log to print data for debugging.
• Asynchronous loading problem: Make sure your asynchronous requests are handled correctly and handle the loading state well.
• Value update problem: Check whether your v-model binding is correct and whether the @change event is handled correctly.

Performance optimization and best practices

For situations where the data volume is large, you can consider using virtual scrolling or lazy loading technology to improve performance. In addition, the code should be written clearly and easily understood and easy to maintain. Don't forget to write comments!

In short, Vue and Element-UI cascade selectors are not complicated by themselves. The key lies in your understanding of Vue data-driven views and control of data structures. Practice more, debug more, and think more, and you can become the controller of the cascading selector. Remember, code is written for people to see and execute by machines, and elegant code is good code.

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