# Leveraging PostgreSQL 16 Enum Types in Rails 7+: A Step-by-Step Guide

If you're a Rails developer, you've probably heard about the recent improvements in Rails 8, including optimizations for SQLite. While I mainly use PostgreSQL for my projects, these updates have piqued my curiosity, and I'm always interested in exploring what's new.

In this article, I'll guide you through leveraging PostgreSQL 16 enums in Rails 7+, showing you how to add an `enum` column to an `article` model, allowing you to define specific categories like `blog`, `snippet`, and `vlog`. Enums offer better data integrity and readability, making your code more maintainable.

## Adding an Enum Column to Your Rails Model

To add a `category` enum column to the `articles` table, start by generating a migration:

```bash
rails g migration AddCategoryToArticles category:string
```

Next, modify the generated migration as follows to create an enum type and assign it to the column:

```ruby
class AddCategoryToArticles < ActiveRecord::Migration[7.2]
  def change
    create_enum :categories, %w[
      blog
      snippet
      vlog
    ]
    add_column :articles, :category, :enum, enum_type: :categories
    add_index :articles, :category
  end
end
```

Run the migration:

```bash
rails db:migrate
```

This will create an enum type called `categories` in PostgreSQL and add a corresponding enum column to the `articles` table. You can verify the change in the schema file, where you'll see both the enum definition and the updated column.

## Defining Enum in Your Model

Now, let's add the enum definition in the `Article` model:

```ruby
class Article < ApplicationRecord
  enum :category, {
    blog: "blog",
    snippet: "snippet",
    vlog: "vlog",
  }, validate: true

  validates :category, presence: true
end
```

The `validate: true` option ensures that the enum is validated automatically with inclusion checks. If the `category` field is required, make sure to backfill existing articles before adding `validates :category, presence: true`.

## Adding a Scope for Filtering by Category

To easily filter articles by their category, you can add a scope to your model:

```ruby
scope :by_category, ->(category) { where(category: category) }
```

This scope allows you to perform queries like `Article.by_category("blog")` to filter articles by a specific category.

## Conclusion

Using PostgreSQL enums in Rails provides type safety and keeps your database schema organized. This approach is particularly useful for fields with a fixed set of values, like categories in a blog or types in a content management system.

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Happy Coding!