DryObjectMapper

Transform your ActiveRecord objects into Dry::Struct DTO objects. Benefits of returning a DTO instead of an ActiveRecord object from your services:

1. It makes our code more readable, we know exactly what fields we are returning, with type safety.
2. It allows us to render the response in any format with ease.
3. It prevents us from accessing the Data Layer directly from the Presentation Layer, rather than going through the Service Layer, preventing accidental queries when accessing data in the views.
4. It works with other tools that i have built, like dry-swagger, which transforms our DTO's into a valid and up to date swagger documentation, with type definitions.

Installation

Add this line to your application's Gemfile:

gem 'dry_object_mapper'

And then execute:

bundle install

Usage

Lets say we have the following Dry::Struct definitions:

class Model3Dto < Dry::Struct
  attribute :description, Types::String
end

class Model2Dto < Dry::Struct
  attribute :name, Types::String
end

class Model1Dto < Dry::Struct
  attribute :id, Types::String
  attribute :age, Types::Integer
  attribute :model2_dto, Model2Dto
  attribute :model3_dto, Types::Array.of(Model3Dto)
end

DryObjectMapper::Mapper.call(model.all, Model1Dto)
=> [
        #<Model1Dto id="22bf569c-f47e-473a-a821-a41b23dae927" 
                    age=25 
                    model2_dto=#<Model2Dto name="Name">
                    model3_dto=[#<Model3Dto description="Description" >]
        >
    ]

If we want to add data that is not present in the model objects, we can pass options as an argument to the call method:

class Model1Dto < Dry::Struct
  attribute :id, Types::String
  attribute :age, Types::Integer
  attribute :some_counter, Types::Integer
  attribute :model2_dto, Model2Dto
  attribute :model3_dto, Types::Array.of(Model3Dto)
end

DryObjectMapper::Mapper.call(model.all, Model1Dto, { some_counter: 10 })
=> [
        #<Model1Dto id="22bf569c-f47e-473a-a821-a41b23dae927" 
                    age=25 
                    some_counter=10
                    model2_dto=#<Model2Dto name="Name">
                    model3_dto=[#<Model3Dto description="Description" >]
        >
    ]

For nested data, pass it as a hash:

class Model2Dto < Dry::Struct
  attribute :name, Types::String
  attribute :some_counter, Types::Integer
end

class Model1Dto < Dry::Struct
  attribute :id, Types::String
  attribute :age, Types::Integer
  attribute :model2_dto, Model2Dto
  attribute :model3_dto, Types::Array.of(Model3Dto)
end

DryObjectMapper::Mapper.call(model.all, Model1Dto, { model2_dto: { some_counter: 10 } })
=> [
        #<Model1Dto id="22bf569c-f47e-473a-a821-a41b23dae927" 
                    age=25 
                    model2_dto=#<Model2Dto name="Name" some_counter=10 >
                    model3_dto=[#<Model3Dto description="Description" >]
        >
    ]

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/dry_object_mapper. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the DryObjectMapper project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.