How To Setup A Project With Ruby On Rails, PostgreSQL And GraphQL

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How To Setup A Project With Ruby On Rails, PostgreSQL And GraphQL

GraphQL is an open source query language created by Facebook. It is a powerful tool that you can use for building your API. It is not a silver bullet but it can definitely help you solve some challenges like getting many resources in a single request. It does not suffer from over-fetching or under-fetching of data and in opposition to the REST API, GraphQL is strongly typed and it is not versioned. In this article, I would like to show you how to setup a Ruby On Rails application with PostgreSQL and GraphQL.


I assume that you have the latest Ruby version available on your computer. Ideally, you installed it through asdf or rvm. I also assume that you have created a gemset for your application. The only other thing that you need is a running PostgreSQL.

As usual with new Rails applications, you have to start with installing a bundler

gem install bundler

and then install the latest rails with this command (which can take a while)

bundle install rails

Finally, we will generate a new rails project

rails new graphql_test --database=postgresql

Remember to set up database.yml and then create a database with

rake db:create

Adding GraphQL

We are going to use the graphql-ruby gem so in your Gemfile you have to add

gem 'graphql' and follow it with bundle install

The next command will be

rails generate graphql:install

which will do a few things:

  • add this line to config/routes.rb

As you probably know, in GraphQL API we define one endpoint which you can use for retrieving or changing data. As you can see this endpoint will be available for us in /graphql path but remember that you have to use the POST method to access it.

  • creates our graphQL controller app/controllers/graphql_controller.rb which will be handling all queries in the execute method:

worth noticing is the way we gather parameters for GraphqlTestSchema.execute method.

  • a lot of base types:
    • base_enum
    • base_input_object
    • base_interface
    • base_object
    • base_scalar
    • base_union
    • mutation_type
    • query_type

we will be using them for constructing mutations, queries, interfaces, and other types

  • adds gem 'graphiql-rails', group: :development to your Gemfile which mounts the GraphiQL IDE that you can use during development. You will have to do bundle install one more time to use it. In routes.rb you will probably notice those lines of codes

Thanks to them you will be able to use /graphiql path to easily test your endpoint locally.

  • adds app/graphql/store_manager_schema.rb that will be you entry point for the whole application

Preparing models and data

Let’s start with those:

bin/rails generate model Author first_name:string last_name:string date_of_birth:date --no-test-framework

bin/rails generate model Book title:string author:references publication_date:integer genre:string --no-test-framework

They will generate migrations that we can run with rake db:migrate. They will also generate models. The only thing that we have to do is add

to app/models/author.rb.

fill in db/seeds.rb with:

and run seeds with rake db:seed

Generates types

As I mentioned before, GraphQL is strongly typed which means that if we want to query for `Author` and `Book` we have to define types for them.



We have a convention that at the top we are adding complex types, followed by ID and at the end simple types like Integer, String etc. As you can see, we are using an enum for the genre. We define enums in a separate directory. app/graphql/types/enums/genre.rb

Defining queries


We defined 4 different queries. Two for collections books and authors, and two for finding book and author using ID. This is actually everything to be able to perform nested queries like:



As you can see, starting a GraphQL project with Ruby On Rails is super easy, therefore, if this is a solution that will solve your problems you shouldn’t stick to REST API and give it a try. In the next articles, I will show you how to define mutations, add authentication, pagination and many more, so stay tuned.

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