mutations.md

Mutations

Mutation for creating blogs

Setting up mutations is as easy as queries, following a very similar process. All GraphQL mutations start from a root type called Mutation. This type is auto generated in the file app/graphql/types/mutation_type.rb.

The only difference is that we are going to create a new mutation class to define our mutation for creating blogs instead of adding it in the root type.

Create a new file app/graphql/mutations/create_blog.rb:

module Mutations
  class CreateBlog < GraphQL::Schema::Mutation
    argument :email, String, required: true, description: "Author's email"
    argument :title, String, required: true
    argument :body, String, required: true

    type Types::BlogType

    def resolve(email:, title:, body:)
      user = User.find_by(email: email)
      return unless user

      Blog.create!(
        title: title,
        body: body,
        user: user
      )
    end
  end
end

Then, we have to expose this new mutation in the root type. If we don't do it, it won't be available in the schema.

Add this in app/graphql/types/mutation_type.rb:

module Types
  class MutationType < BaseObject
    field :create_blog, mutation: Mutations::CreateBlog, description: 'Create new blog'
  end
end

To test it, just restart the server and use GraphiQL.

Extra mile

What if creating a blog implies sending a lot of params? Is there a way to refactor this mutation? Or should we still send them separate and catch them one by one using keyword arguments?