QueryExtensions

README.md

QueryExtensions

First, you'll need to incorporate the extension:

class ApplicationRecord < ActiveRecord::Base
  extend QueryExtensions
end

Now, you can use it like this:

class Author < ApplicationRecord
end

Author.where_has { age.eq(29).or(age.gt(40)) }
# SELECT "authors".* FROM "authors" WHERE ("authors"."age" = 29 OR "authors"."age" > 40)

Author.joins(:posts).where_has { Post[:title].matches("Breaking News:%") }
# SELECT "authors".* FROM "authors" INNER JOIN "posts" ON "posts"."author_id" = "authors"."id" WHERE "posts"."title" LIKE 'Breaking News:%'

In the example above, age and Post[:title] are instances of Arel::Attributes::Attribute.

query_extensions.rb

module QueryExtensions
  def [](name)
    arel_table[name]
  end

  def where_has(&block)
    where DSL.new(self).evaluate(&block)
  end

  def selecting(&block)
    select DSL.new(self).evaluate(&block)
  end

  def ordering(&block)
    order DSL.new(self).evaluate(&block)
  end
  
  class DSL
    def initialize(model)
      @model = model
    end

    def evaluate(&block)
      if block.arity.zero?
        instance_eval(&block)
      else
        instance_exec(self, &block)
      end
    end

    private

    def respond_to_missing?(name, *)
      @model.column_names.include?(name.to_s) || super
    end

    def method_missing(name, *args, &block)
      if @model.column_names.include?(name.to_s)
        @model.arel_table[name]
      else
        super
      end
    end
  end
end