Rails : serve dummy data via graphql using ActiveModel and json file

31 Oct 2018

Graphql is a alternative to REST architecure which allows client to request the data in particular stucture and it returs data in thbe same structure.

When you work as a Frontend and Backend team, you might need to setup a server to serve dummy data so that Frontend team can work in parallel.

This post assumes that we already have a bootstrapped project with rails and graphql-ruby. Consider we have some data of users

[
    {
        "id":1,
        "name": "Leanne Graham",
        "username": "Bret",
        "email": "Sincere@april.biz"
    },
    {
        "id": 2,
        "name": "Ervin Howell",
        "username": "Antonette",
        "email": "Shanna@melissa.tv"
    },
    {
        "id": 3,
        "name": "Clementine Bauch",
        "username": "Samantha",
        "email": "Nathan@yesenia.net"
    },
    {
        "id": 4,
        "name": "Patricia Lebsack",
        "username": "Karianne",
        "email": "Julianne.OConner@kory.org"
    }
]

To serve this through the graphql query first we need to setup the UserType.

# app/graphql/types/user_type.rb
module Types
  class UserType < Types::BaseObject
    graphql_name 'User'

    field :id, ID, null: false
    field :name, String, null: false
    field :username, String, null: false
    field :email, String, null: false
  end
end

Then lets setup the User model using ActiveModel

# app/model/user.rb
class User
  include ActiveModel::Serializers::JSON

  attr_accessor :name, :id, :username, :email
  
  def attributes=(hash)
    hash.each do |key, value|
      send("#{key}=", value)
    end
  end
  
  def attributes
    instance_values
  end
end

Setup collection query type

Next, the crucial part on setting the QueryType with custom resolver.

# app/graphql/types/query_type.rb

require 'json'

module Types
  class QueryType < Types::BaseObject

    field :users, [UserType], null: false, resolve: -> (obj, args, ctx) {
        file = File.read File.join(File.dirname(__FILE__), "../data/users.json")
        data = JSON.parse(file)
    
        data.map do |user|
          g = User.new
          g.from_json(user.to_json)
        end
      }
  end
end

Now in your /graphiql interface when you query for

{
  users {
    id,
    name
  }
}

you will receive the response

collection response

Setup single record query type

Since we already have the UserType and User model we need to add only query type to respond for single record requests.

# app/graphql/types/query_type.rb

require 'json'

module Types
  class QueryType < Types::BaseObject

    field :user, UserType,
        null: false,
        resolve: -> (obj, args, ctx) {
          file = File.read File.join(File.dirname(__FILE__), "../data/users.json")
          data = JSON.parse(file)
          selectedUser = data.select do |user|
            user['id'].to_i == args[:id]
          end.first
          user = User.new
          user.from_json(selectedUser.to_json)
          
        } do
          argument :id, Int, required: true
    end
end

The record response will be

record response

The code is available on revathskumar/rails-graphql-activemodel-json

Versions of Language/packages used in this post.

| Library/Language | Version         |
| ---------------- |-----------------|
|      rails       |  5.2.1          |
|      ruby        |  2.6.0-preview2 |
|  graphql (gem)   |  1.8.11         |
|  graphql-rails   |  1.4.11         |
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