How to Set a Field Value with the Same Document ID in Mongoose

Описание: Learn how to automatically set a field value to match the document ID in Mongoose using pre-hook middleware. This guide walks you through the solution step-by-step!
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How to Set a Field Value with the Same Document ID in Mongoose

When working with databases, particularly MongoDB in Node.js with Mongoose, you might encounter a scenario where you want a specific field in your documents to mirror the document’s ID. This can be a bit tricky, especially if you want to ensure that the field’s value is always consistent with the document ID. In this guide, we’ll explore a simple solution that tackles this problem effectively.

The Problem

Suppose you have a Mongoose schema where you want a certain field, say linkId, to hold the same value as the document's automatically generated ID, _id. Here's an illustration of the desired output:

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In the example above, you can see that both _id and linkId hold the same string value. While this may seem redundant, there are valid use cases for having this structure. So how can we set this up when creating new documents in Mongoose?

The Solution

To achieve our goal, we will utilize pre-hook middleware. Mongoose provides this feature that allows you to define a function that runs before certain events, such as saving a document. By leveraging this, we can set the linkId field to automatically match the value of _id before the document is saved to the database.

Step-by-Step Implementation

Here’s how you can implement it step by step:

1. Define Your Schema

First, you will need to create your Mongoose schema. Here’s an example of how you might structure it:

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2. Add Pre-Hook Middleware

Next, add the pre-save middleware to your schema. This is where the magic happens. The middleware will set the linkId to be equal to _id whenever you save a new document.

[[See Video to Reveal this Text or Code Snippet]]

3. Finalizing Your Model

After defining the schema and the middleware, you can then create and export your Mongoose model:

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4. Saving a New Document

Now you can create and save new documents without worrying about manually setting the linkId every time:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By using Mongoose's pre-hook middleware, you can effortlessly keep the linkId field in sync with the document’s _id. This not only simplifies your code but also speeds up your development process by reducing redundancy. Whether this structure serves a specific functionality in your application or keeps your data organized, you’ve now got a clear path to achieving a consistent document structure in your MongoDB database.

Feel free to dive into Mongoose’s documentation for more advanced functionalities and start implementing clean, consistent database schemas in your projects!