Rails Scopes: Create Faster, Cleaner Queries

With the use of scopes, a developer can create a fast query and add additional methods like pluck that would otherwise throw an error.

Why use Scopes?

Scopes allow a developer to create reusable code instead of a method in the controller. Scopes also return an ActiveRecord::Relation object, opening the door for combining multiple scopes.

Let's look at one example where scopes are better:

def member_ids
	member_emails = ['john.smith@example.com', 'm.jackson@example.com', 'bob.smith@exmple.com']

Account.where(email: member_emails)
end

How to Create:

scopes are created inside a method. While not required, adding additional arguments is possible.

Ex:

scope :name_for_method, →(arguments NOT required) {query is inserted here!}

# Grab all users with a certain role (roles is an array) 
scope :admin, { where('? = ANY(roles)', 'Admin') }

This will allow using the method globally for the class. A class in Ruby is a controller. It also has methods.

```ruby
@group.announcements.manager_all_messages(current_user)
```

Or grab all accounts with a certain role. This is created inside the method file for your Ruby class.

def admin
  Account.admin.pluck(:id)
end

Conclusion:

Scopes provide cleaner code and remove the need for multiple class methods. They also allow combining multiple scopes and do not contain overly complicated logic.

Resources:

https://guides.rubyonrails.org/action_controller_overview.html#what-does-a-controller-do-questionmark