Speaker Mutations - non-nullable - [Post] GraphQL with Sinatra (Ruby) - Part 2- Mutations

speaker_mutations5.rb

module SpeakerMutations
  Create = GraphQL::Relay::Mutation.define do
    name 'CreateSpeaker'
    description 'Creates a speaker'

    input_field :name, !types.String # note the !
    input_field :bio, types.String
    input_field :twitterHandle, types.String
    input_field :talkTitle, !types.String

    # ... rest of the mutation body
  end
end