Getting Started

Installation

You can install graphql from RubyGems by adding to your application’s Gemfile:

# Gemfile
gem "graphql"

Then, running bundle install:

$ bundle install

Getting Started

On Rails, you can get started with a few GraphQL generators:

# Add graphql-ruby boilerplate and mount graphiql in development
rails g graphql:install
# Make your first object type
rails g graphql:object Post title:String rating:Int comments:[Comment]

Or, you can build a GraphQL server by hand:

Define some types
Connect them to a schema
Execute queries with your schema

Declare types

Types describe objects in your application and form the basis for GraphQL’s type system.

# app/graphql/types/post_type.rb
module Types
  class PostType < Types::BaseObject
    description "A blog post"
    field :id, ID, null: false
    field :title, String, null: false
    # fields should be queried in camel-case (this will be `truncatedPreview`)
    field :truncated_preview, String, null: false
    # Fields can return lists of other objects:
    field :comments, [Types::CommentType], null: true,
      # And fields can have their own descriptions:
      description: "This post's comments, or null if this post has comments disabled."
  end
end

# app/graphql/types/comment_type.rb
module Types
  class CommentType < Types::BaseObject
    field :id, ID, null: false
    field :post, PostType, null: false
  end
end

Build a Schema

Before building a schema, you have to define an entry point to your system, the “query root”:

class QueryType < GraphQL::Schema::Object
  description "The query root of this schema"

  # First describe the field signature:
  field :post, PostType, null: true do
    description "Find a post by ID"
    argument :id, ID, required: true
  end

  # Then provide an implementation:
  def post(id:)
    Post.find(id)
  end
end

Then, build a schema with QueryType as the query entry point:

class Schema < GraphQL::Schema
  query QueryType
end

This schema is ready to serve GraphQL queries! Browse the guides to learn about other GraphQL Ruby features.

Execute queries

You can execute queries from a query string:

query_string = "
{
  post(id: 1) {
    id
    title
    truncatedPreview
  }
}"
result_hash = Schema.execute(query_string)
# {
#   "data" => {
#     "post" => {
#        "id" => 1,
#        "title" => "GraphQL is nice"
#        "truncatedPreview" => "GraphQL is..."
#     }
#   }
# }

See Executing Queries for more information about running queries on your schema.

Use with Relay

If you’re building a backend for Relay, you’ll need:

A JSON dump of the schema, which you can get by sending GraphQL::Introspection::INTROSPECTION_QUERY
Relay-specific helpers for GraphQL, see the GraphQL::Relay guides.

Use with Apollo Client

Apollo Client is a full featured, simple to use GraphQL client with convenient integrations for popular view layers. You don’t need to do anything special to connect Apollo Client to a graphql-ruby server.

Use with GraphQL.js Client

GraphQL.js Client is a tiny client that is platform- and framework-agnostic. It works well with graphql-ruby servers, since GraphQL requests are simple query strings transported over HTTP.