Скачать или смотреть Understanding Vue 3 Object Reference Comparison with Proxy

Learn how to efficiently compare object references in `Vue 3` when using reactive arrays and proxies. This blog explores solutions and best practices for managing data in Vue components.
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Understanding Vue 3 Object Reference Comparison with Proxy: A Quick Guide

When working with Vue 3, developers often encounter issues related to object references, particularly when dealing with reactive properties and proxies. A common problem arises when you need to compare a regular object with a reactive object and find that the comparison returns false. This post explains why this happens and provides effective solutions to address the challenge of comparing object references in Vue 3.

The Problem Explained

Consider a scenario where you have a parent and a child component. You bind an array of objects, tags, to a child component and maintain a second array, selectedTags, that populates based on user interaction. The core issue occurs when you attempt to compare the original object from the tags array to the object in the selectedTags array after making a selection. The comparison fails despite the expectation that they refer to the same object.

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Why Does This Happen?

The reason the comparisons yield false is due to the nature of Vue’s reactivity system:

tags is a regular non-reactive array.

selectedTags is a reactive reference, meaning it is wrapped in a Proxy instance.

When you push tags[0] into selectedTags, the reference is preserved, but the underlying object is transformed into a reactive object, thus changing its identity.

Attempting to Access the Proxy's Target

Even attempts to access the target of the proxy or using .value yield similar results. The following comparisons also result in false:

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A Practical Solution

Using toRaw to Retrieve the Original Object

To compare the original object without the proxy wrapping, you can use the toRaw method, which returns the raw version of the reactive object:

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Keeping Reactivity Consistent

To prevent this issue in the future, ensure that both the tags and selectedTags properties are defined with consistent reactivity. This can be achieved in a couple of ways:

Reactive Arrays: Define both properties as deeply reactive arrays using reactive or readonly.

Shallowly Reactive Arrays: Alternatively, you can define them as shallowly reactive arrays using shallowReactive, or mix both reactive and non-reactive definitions using markRaw.

Compare by Identifier Instead of Reference

A good practice in such cases is to compare objects by unique identifiers, rather than comparing the actual object references:

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Avoiding Prop Mutation

It’s important to note that mutating props directly in child components is generally discouraged as it complicates data flow. Instead, children should emit events to parents to update state:

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Conclusion

In summary, comparing object references in Vue 3 can be tricky when proxy wrappers and reactive arrays come into play. By utilizing methods like toRaw, ensuring consistent reactivity, and comparing properties like id, developers can effectively manage data and avoid common pitfalls. Remember to always follow best practices by avoiding mutation of props to keep your component structures clean and predictable.

Thus, tackling similar issues in Vue will become easier with a better understanding of reactivity and properties, paving the way for more robust and maintainable code.