Causes and solutions for data loss due to reactive use

1. The trap of direct assignment

In Vue's responsive system,reactiveObject is a deep proxy that tracks changes in object properties, but if you reassign the entire object, then Vue cannot continue to track new objects. This is because Vue's responsive mechanism does not support direct replacement of the entire object.

Example:

import { reactive } from 'vue';

const state = reactive({
  user: {
    name: 'John',
    age: 30
  }
});

// Error example: Direct assignment = {
  name: 'Jane',
  age: 25
}; // Vue cannot track this assignment operation, the view will not be updated

In the above example,Reassigned as a new object. AlthoughuserThe new attribute of , will exist in memory, but Vue cannot detect such direct assignment, so the view will not be updated.

2. The correct way to do it

2.1 Update data using the methods provided by Vue

Vue recommends that you use the methods provided by Vue's responsive API to update the properties of an object, rather than directly replacing the entire object. This ensures that Vue's responsive system can track and update data correctly.

Example:

import { reactive, set } from 'vue';

const state = reactive({
  user: {
    name: 'John',
    age: 30
  }
});

// Correct way: Use the method provided by Vue to update properties = 'Jane'; // Correct, the view update will be triggered = 25; // Correct, the view update will be triggered

2.2 Use Merge Objects

If you need to update multiple properties of the object, you can useor other similar merge methods to update the object instead of directly replacing the entire object.

Example:

import { reactive } from 'vue';

const state = reactive({
  user: {
    name: 'John',
    age: 30
  }
});

// Merge update: stay responsive(, {
  name: 'Jane',
  age: 25
}); // Correct, the view update will be triggered

2.3 Use (Applicable to Vue 2)

In Vue 2, you can useMethod to ensure that new responsive attributes are added. But in Vue 3, this method has been deprecated and used insteadreactive�

Example (Vue 2):

import Vue from 'vue';

const state = ({
  user: {
    name: 'John',
    age: 30
  }
});

// Usage of Vue 2(, 'name', 'Jane'); // Correct, the view update will be triggered

3. Handle nested objects

If yourreactiveObjects contain nested objects. You need to be careful to avoid directly replacing nested objects, but modifying their properties.

Example:

import { reactive } from 'vue';

const state = reactive({
  user: {
    profile: {
      name: 'John',
      age: 30
    }
  }
});

// Error example: Replace nested objects directly = {
  name: 'Jane',
  age: 25
}; // Vue cannot track this assignment operation, the view will not be updated
// Correct example: Modify properties of nested objects = 'Jane'; // Correct, the view update will be triggered = 25; // Correct, the view update will be triggered

4. Summary

Give it directlyreactiveAssigning attributes to objects will cause Vue to fail responsively, so this operation needs to be avoided. By updating properties or merging objects using methods provided by Vue, you can ensure correctness of responsive data and synchronous updates of views. Understanding and following these principles during development can help you avoid common pitfalls and improve application stability and maintainability.

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