GraphQL Api With Rails

Graphql is an awesome new technology which is making it easier for client
side developers to iterate quickly and batch together network requests.

I really like the promise provided by GraphQl however it is not as easy
as rest to get up and running on immediately. This blog post takes a look
at how to build a working GraphQL backend in just a few steps using rails.

I am using my own project graphql-api as a framework for building out the GraphQL backend.

We will look at building a basic blogging application. A blog will have
an author and some tags.

First create the rails backend.

rails new blog-api --api

Add the necessary libraries to the Gemfile

gem 'graphql'
gem 'graphql-api'

Create our models

rails g model Author name:string
rails g model Blog title:string content:text author:references
rails db:migrate

Add our has many relations to author class

class Author
  has_many :blogs
end

Great! Now we have a basic setup for our blogging backend. Let's add some
controllers to serve basic Graphql queries.

Add the following file to app/controllers/graphql_controller.rb.

class GraphqlController < ApplicationController
  SCHEMA = GraphQL::Api::Schema.new.schema
  def create
    render json: SCHEMA.execute(
      params[:query], 
      variables: params[:variables] || {},
    )
  end

end

Add the following route to config/routes.rb

resources :graphql, only: :create

Now let's test out the new api with curl. Start up the server and run the
following command to see if we have any blog posts

curl -XPOST -d 'query=query { blogs { id } }' \
     localhost:3000/graphql
{"data":{"blogs":[]}}

Let's create an author

curl -XPOST \
  -d 'query=mutation { 
         createAuthor(input: {name: "foobar"}) { 
            author { id } 
     }}' localhost:3000/graphql
{"data":{"createAuthor":{"author":{"id":1}}}}

Now let's create a blog with that author's id

curl -XPOST \
  -d 'query=mutation { 
         createBlog(input: {title: "foobar", author_id: 1}) { 
             blog { id } 
      }}' localhost:3000/graphql
{"data":{"createBlog":{"blog":{"id":1}}}}

Let’s try that first query again, but this time let’s try and return the blog authors as well as the blog name.

curl -XPOST -d 'query=query { 
        blogs { 
          id
          title
          content
          author {
            name
          }
        }
     }' localhost:3000/graphql

You can also run updateBlog mutations as well as updateAuthor mutations. Try deleting an author or blog and see what responses you get back.

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