GraphQL-Pro CanCan integration example

can_can_graphql.rb

require "bundler/inline"

gemfile do
  gem "graphql", "2.3.4"
  gem "graphql-pro", "1.27.5"
  gem "cancancan", "3.5.0"
end

class Ability
  include CanCan::Ability

  def initialize(viewer)
    can :check_balance, User do |user|
      can_check_balance = user == viewer || viewer.superuser
      puts "Can check_balance? #{can_check_balance} (#{user == viewer}, #{viewer.superuser})"
      can_check_balance
    end
  end
end

User = Struct.new("User", :superuser, :account_balance)

class MySchema < GraphQL::Schema
  class BaseField < GraphQL::Schema::Field
    include GraphQL::Pro::CanCanIntegration::FieldIntegration
    can_can_action(nil) # default to no auth
  end

  class BaseObject < GraphQL::Schema::Object
    include GraphQL::Pro::CanCanIntegration::ObjectIntegration
    field_class(BaseField)
    can_can_action(nil) # default to no auth
  end

  class User < BaseObject
    field :account_balance, Int, can_can_action: :check_balance
  end

  class Query < BaseObject
    field :user, User

    def user
      ::User.new(false, 100)
    end

    field :current_user, User

    def current_user
      context[:current_user]
    end
  end

  query(Query)
end

query_str = "{ user { accountBalance } }"

pp MySchema.execute(query_str, context: { current_user: User.new(true, 0) }).to_h
# Can check_balance? true (false, true)
# {"data"=>{"user"=>{"accountBalance"=>100}}}

pp MySchema.execute(query_str, context: { current_user: User.new(false, 0) }).to_h
# Can check_balance? false (false, false)
# {"data"=>{"user"=>{"accountBalance"=>nil}}}

pp MySchema.execute("{ currentUser { accountBalance } }", context: { current_user: User.new(false, 55) }).to_h
# Can check_balance? true (true, false)
# {"data"=>{"currentUser"=>{"accountBalance"=>55}}}