using ActiveRecord::PredicateBuilder.register_handler

ar_opts.rb

module AROpts

  module Helpers
    def GT(val); AROpts::GT.new(val); end
    def LT(val); AROpts::LT.new(val); end
    def GTE(val); AROpts::GTE.new(val); end
    def LTE(val); AROpts::LTE.new(val); end
  end

  GenericOp = Struct.new(:expression)

  class GT < GenericOp; end
  class LT < GenericOp; end
  class GTE < GenericOp; end
  class LTE < GenericOp; end

  def self.register!
    ActiveRecord::PredicateBuilder.register_handler(GT, proc { |column, op| Arel::Nodes::GreaterThan.new(column, op.expression) })
    ActiveRecord::PredicateBuilder.register_handler(LT, proc { |column, op| Arel::Nodes::LessThan.new(column, op.expression) })
    ActiveRecord::PredicateBuilder.register_handler(GTE, proc { |column, op| Arel::Nodes::GreaterThanOrEqual.new(column, op.expression) })
    ActiveRecord::PredicateBuilder.register_handler(LTE, proc { |column, op| Arel::Nodes::LessThanOrEqual.new(column, op.expression) })
  end
end

AROpts.register!
include AROpts::Helpers
Payment.where(total_cents: LTE(1000)).first