Alex's Slip-box

These are my org-mode notes in sort of Zettelkasten style

ActiveRecord query objects

Created on August 16, 2024

Updated on August 28, 2024

Tags: rails

:ID: 59ED4C2F-6166-4277-B3B5-3BAF6E8929F6

Isolate business logic from models.

See also ActiveRecord Querying

# Base class

# app/models/application_query.rb
class ApplicationQuery
  def self.call(...)
    new.resolve(...)
  end

  attr_reader :relation

  def initialize(relation)
    @relation = relation
  end

  def resolve(*args)
    relation
  end
end

# Subclass example

This is from tmp 

# app/models/user/with_image_containing_memos.rb
class User
  class WithImageContainingMemos < ApplicationQuery
    def initialize(relation = User.all)
      super(relation)
    end

    def resolve(image_count: 1)
      User.with(
        with_image_memos: Memo.where(image_attachment_count: image_count..)
                              .select(:user_id)
                              .distinct
      ).joins(:with_image_memos)
    end
  end
end

# Adding scopes

One could decide to extract scopes used for a query object to the relevant model. Or they could be extracted to a module within the query object as a way of wrapping parts of the query in methods that organize the code and improve readabilty. 

# app/models/user/with_image_containing_memos.rb
class User
  class WithImageContainingMemos < ApplicationQuery
    module Scopes
      def with_image_count_gt(count)
        where(image_attachment_count: image_count..)
      end
    end

    def initialize(relation = User.all)
      super(relation)
    end

    def resolve(image_count: 1)
      User.with(
        with_image_memos: Memo.extending(Scopes)
                              .with_image_count_gt(image_count)
                              .select(:user_id)
                              .distinct
      ).joins(:with_image_memos)
    end
  end
end

# Attach query obj to scope

Query objects can be attached to active record scopes if you want, as long as the object responds to call 

class User < ApplicationRecord
  scope :with_image_containing_memos, WithImageContainingMemos
end

Search Results