How To Use Scopes In ActiveRecord Rails

Scopes in ActiveRecord Rails are a powerful feature that allow you to define pre-defined queries that can be easily reused throughout your application. In this article, we will explore how to use scopes in ActiveRecord Rails to make your code more readable and maintainable.

What are Scopes?

Scopes are essentially named queries that can be defined on a model in Rails. They allow you to encapsulate common query logic into a reusable method that can be called on the model itself. This can help to keep your code DRY (Don't Repeat Yourself) and make it easier to read and maintain.

Defining Scopes

To define a scope on a model in Rails, you simply use the scope method followed by the name of the scope and a lambda that defines the query logic. For example:

class Post < ApplicationRecord
  scope :published, -> { where(published: true) }
end

In this example, we have defined a scope called published that returns all posts where the published attribute is set to true.

Using Scopes

Once you have defined a scope on a model, you can easily use it in your code by simply calling the scope method on the model. For example:

published_posts = Post.published

This will return all posts that are published, making it much easier to query for specific subsets of data without having to write out the full query each time.

Chaining Scopes

One of the great things about scopes in Rails is that you can chain them together to create more complex queries. For example:

recent_published_posts = Post.published.where('created_at > ?', 1.week.ago)

In this example, we are chaining the published scope with a where clause to find all posts that are published and were created within the last week.

Default Scopes

In addition to regular scopes, Rails also allows you to define default scopes on a model. Default scopes are applied to every query that is made on the model, unless explicitly overridden. For example:

class Post < ApplicationRecord
  default_scope { order(created_at: :desc) }
end

In this example, we have defined a default scope that orders all posts by their created_at attribute in descending order. This means that every query made on the Post model will automatically be ordered by created_at unless a different order is specified.

Conclusion

Scopes in ActiveRecord Rails are a powerful tool that can help you write cleaner and more maintainable code. By encapsulating common query logic into reusable methods, you can make your code more readable and DRY. So next time you find yourself writing the same query over and over again, consider using a scope to simplify your code.