Ensuring Unique Boolean Keys for Campaigns in Mongoose with Pre-Save Middleware

Learn how to set up unique boolean validation for teams in your Mongoose schemas to avoid duplicate default teams in the same campaign.
---
This video is based on the question https://stackoverflow.com/q/67626431/ asked by the user 'Mendi Sterenfeld' ( https://stackoverflow.com/u/8266703/ ) and on the answer https://stackoverflow.com/a/67628722/ provided by the user 'amda' ( https://stackoverflow.com/u/14979932/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Mongoose: only one unique boolean key should be true

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Ensuring Unique Boolean Keys for Campaigns in Mongoose with Pre-Save Middleware

When working with a database schema that includes boolean flags, you might face a challenge: ensuring that only one team per campaign can have a unique boolean value set to true. In this guide, we'll tackle a common problem that developers encounter when designing schemas in Mongoose, particularly focusing on the isDefault field in teams associated with various campaigns.

Problem Statement

Suppose you have two collections in your MongoDB: Campaigns and Teams. Each team can be marked as a default for its respective campaign using a boolean field called isDefault. The requirement is clear: you should only allow one team to be isDefault: true for any given campaignId. Trying to add multiple default teams leads to conflicts, and your application should throw an error to prevent this situation. Here’s what we want to avoid:

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

To implement this check effectively, we can utilize Mongoose's middleware functionality. Let's break down how to achieve this.

Solution: Using Pre-Save Middleware

Summary of the Approach

The simplest way to enforce the uniqueness requirement is to use Mongoose's pre('save') middleware. This allows us to check the presence of a default team in the collection before actually saving the new or modified entry. If a default team is found, we will throw an error, stopping the save operation.

Step-by-Step Implementation

Here is how you can implement this solution:

Define Your Schemas: Ensure your basic schemas for Campaigns and Teams are set up correctly.

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

Implement the Pre-Save Hook: Add a pre('save') hook to your TeamSchema to check for existing default teams.

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

Explanation of the Middleware

this.isNew: Checks if the current document is new, meaning it hasn't been saved to the database yet.

this.isModified("isDefault"): Checks if the isDefault field has been modified.

await mongoose.models["Team"].findOne({...}): Searches for an existing team that fulfills both conditions of having isDefault set to true and matching the given campaignId.

Throwing an error: If a previous default team exists for the same campaign, an error is thrown to stop the saving operation.

Conclusion

By implementing this simple yet effective solution, you can ensure that your application adheres to the constraint of having only one default team per campaign. This method offers a seamless way to prevent unwanted duplicates and maintain data integrity in your MongoDB collections.

If you've been struggling with managing boolean flags in a schema or simply looking to enhance your validation methods, Mongoose middleware provides powerful tools to address these challenges effectively.

By following the steps outlined above, you’ll be on your way to creating robust and reliable database models in your applications.

Видео Ensuring Unique Boolean Keys for Campaigns in Mongoose with Pre-Save Middleware канала vlogize