This should help you to install graphql and setup the basics on any new rails application.

  • Adds Graphql gem and runs the graphql installer
  • Copies the grapqhl schema template which has the rescue block configured.
  • Certain files like grapqhl query, input and exceptions are inside the gem, which makes the listing of records easier.


Add the gem to the Gemfile

gem 'cm-graphql'


If this is the first time graphql is getting added to the project, run the following generator

rails g cm_graphql:add_graphql

This will run the graphql generator graphql:install and copy the graphql schema template.


Another generator to help you get started with a basic list endpoint is

rails g cm_graphql:list_api model_name
rails g cm_graphql:list_api course

# Sample grapqhl request

query {
    courses(paging: {
        pageNo: 1
        perPage: 100
    }) {
        paging {
        data {

This will add the necessary files to the application.

  • course_list_type
  • course_type
  • course_query

Mount the engine at

mount CmGraphql::Engine => "/cm-graphql"

And you are done, you can test out the pagination.

Explaination on how this works.

  1. Kaminari Gem has page and per methods. These methods are used to set the page no and records per page of a model.
  2. The paging Input type in app/graphql/types/inputs/base/paging.rb exposes a interface to the frontend where the frontend can enter page no and records per page.
  3. The query uses a list method on the model. This method is inherited by the model from the paginator concern.
  4. We apply the kaminari method in the list method to apply pagination to the model.
  5. The paginator then calls the filtered_list model to arrange the model data and paging data in a representable way. This helps us make sure all the pagination follow the same pattern for data representation.
  6. The paging_type in app/graphql/types/objects/base/paging_type.rb is used to represent the paging data to the frontend.
  7. The pagination and model data is represented with object type in app/graphql/types/objects/example_list_type.rb.
  8. And we have successfully applied pagination to our graphql project.