How to use Polymorphic Associations in Ruby on Rails?

Introduction

In Ruby on Rails, a polymorphic association allows a model to belong to more than one other model on a single association. This can be useful in situations where you want to associate a single model with multiple types of models, without having to create separate associations for each type.

The Problem

Consider the following scenario: you are building a social media application and you want to create a `Like` feature that allows users to like posts and comments.

In a traditional one-to-many association, you would need to create separate models for each type of `likeable` object (e.g., PostLike, CommentLike), and each model would have a foreign key pointing to the corresponding `likeable` object. This can get messy and difficult to maintain, especially as your application grows in complexity.

The problem with using multiple join tables to model many-to-many relationships is that it can become difficult to query and update the data. You may need to write complex SQL queries to retrieve the data you need, or use multiple Active Record associations to traverse the relationships. This can be time-consuming and error-prone, especially if you have multiple levels of relationships between models.

The Solution

To solve this problem, we can use polymorphic associations in Ruby on Rails. This allows us to define a single association that can belong to multiple models, without having to write extra code to handle the different types of content.

Here is how to set up a polymorphic association in Rails:

• Add a likeable_id and a likeable_type column to the likes table. These columns will be used to store the ID and type of the content that is being liked.

• Define a polymorphic association in the Like model by using the belongs_to method, and passing the :likeable option. This tells Rails that the Like model can belong to any model that is specified as the value of the :likeable option.

• In the models for the different types of content that can be liked (e.g. Post and Comment), define a reverse association by using the has_many method and passing the :likes option. This allows us to access the likes for a particular piece of content.

With this in place, we can now associate a Like with either a Post or a Comment, using a single association. For example:

Conclusion

Polymorphic associations in Ruby on Rails can be a powerful tool for simplifying many-to-many relationships between models. By using a single association, you can avoid the complexity and maintenance issues of multiple join tables. This can make it easier to query and update your data, and can help you build more flexible and scalable applications.

The polymorphic association allows you to easily add comments to any model that you want, without having to define separate associations for each model. This can make your code more DRY (don’t repeat yourself) and easier to maintain.

By using the steps outlined above, you can easily set up polymorphic associations in your own Rails application and start taking advantage of the benefits they offer.

In conclusion, polymorphic associations are a powerful and flexible way to handle complex model relationships in Ruby on Rails.

I hope you enjoyed reading. ✌️ I wish you happy coding. 👨‍💻