create_sandbox

# File railties/lib/rails_generator/generators/components/scaffold/scaffold_generator.rb, line 160
    def create_sandbox
      sandbox = ScaffoldingSandbox.new
      sandbox.singular_name = singular_name
      begin
        sandbox.model_instance = model_instance
        sandbox.instance_variable_set("@#{singular_name}", sandbox.model_instance)
      rescue ActiveRecord::StatementInvalid => e
        logger.error "Before updating scaffolding from new DB schema, try creating a table for your model (#{class_name})"
        raise SystemExit
      end
      sandbox.suffix = suffix
      sandbox
    end