Ruby有没有办法阻止用户在访问不同的函数/过程之前通过case调用函数/过程？

module MyModule
  private

  def self.method_missing(method_name, *args, &block)
    raise NoMethodError, "undefined method `#{method_name}' for #{self}:Module"
  end
end

class MyClass
  extend MyModule

  def self.function1
    puts "Function 1"
  end

  def self.function2
    puts "Function 2"
  end

  def self.function3
    puts "Function 3"
  end
end

case choice
when 1
  MyClass.function1
when 2
  MyClass.function2
else
  MyClass.function3
end