Hanami Repository Dynamic Ordering Sort database records with parametrized order policy

Hanami Repository Dynamic Ordering

If you want to support records sorting based on user input. Imagine clicking a column to sort field to be ascending or descending.

The Hanami::Model::Sql module exposes .asc and .desc methods to generate a SORT ASC or DESC sort policy. You want to dynamically invoke one of these methods, based on the value of direction, by using public_send. For security reasons, we want to whitelist the allowed values of direction. Otherwise, any method can be invoked on Hanami::Model::Sql.

Finally we use the dynamic block accepted by #order to set the sorting policy.

# lib/bookshelf/repositories/post_repository.rb
# frozen_string_literal: true

class PostRepository < Hanami::Repository
  def sort_by(column, direction)
    unless ORDER_DIRECTIONS.include?(direction.to_sym)
      message = "unknown direction: #{direction.inspect}"
      raise ArgumentError.new(message)
    end

    policy = Hanami::Model::Sql.public_send(direction, column.to_sym)
    posts.order { policy }
  end

  ORDER_DIRECTIONS = %i[asc desc].freeze
  private_constant :ORDER_DIRECTIONS
end