What should I do if the value of the uniapp list cannot be modified?

Recently, when I was using uniapp to develop a mobile application, I encountered a problem that had troubled me for a long time: in the list, its value cannot be modified.

In order to solve this problem, I first carefully checked the documents and related information, but did not find a direct solution. So, I started troubleshooting the problem step by step and finally identified the problem.

First, I checked the code and found that my list rendering uses the v-for instruction. The code is as follows:

<view>
  <text>{{ item }}</text>
  <button>编辑</button>
</view>

As you can see, I used a button element to trigger the editing operation. , and the index of the current item is passed in.

The next step is the implementation of my editItem method:

editItem(index) {
  this.list[index] = 'new value'
}

Among them, I try to use index to modify the value at the corresponding position.

However, when I click the edit button, the values ​​on the list remain unchanged no matter how I modify them. I tried many times but couldn't solve this problem.

Finally, I discovered the problem: since uniapp uses virtual DOM technology, modifications to components or elements need to be implemented through Vue's responsive system. When I used index to directly modify the value of the array item, it violated Vue's "data-driven view" principle, which resulted in the inability to update the list.

The solution is also very simple: I only need to use the set method provided by Vue to update the value at the corresponding position, and the list can be updated correctly.

The final code implementation is as follows:

editItem(index) {
  Vue.set(this.list, index, 'new value')
}

After this debugging, I have a deep understanding of the principles of uniapp and Vue's responsive system, and I have become more proficient in Vue's data manipulation methods.

In short, if you encounter similar problems in uniapp, you can consider checking whether it violates Vue's responsiveness principle, and then take appropriate measures to solve the problem.

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