ruby - 如何在 ruby​​ 中只发出一次警告？

Question

是否可以告诉 ruby​​ 只发出一次警告，而不是多次发出警告？

class SoylentGreen
  def eat
    warn "Algae harvesting not implemented. Soylent green is people!"
  end
end

5.times do
  soylent_green = SoylentGreen.new
  soylent_green.eat
end

产生

Algae harvesting not implemented. Soylent green is people!
Algae harvesting not implemented. Soylent green is people!
Algae harvesting not implemented. Soylent green is people!
Algae harvesting not implemented. Soylent green is people!
Algae harvesting not implemented. Soylent green is people!

而理想情况下，我希望它只发生一次。

我没有使用 Rails，但可以访问 ruby​​ 1.8 和 1.9。

备选方案包括编写我自己的警告系统(它只涵盖像这样的故意警告)，或者将警告放在 SoylentGreen#eat 之外(这会导致它显示，即使该方法未被调用)。

Answer 1

基于混沌的回答..

class SoylentGreen
  def eat
    warn_once "Algae harvesting not implemented. Soylent green is people!"
  end
  def warn_once(msg)
    @@warned||=false
    if not @@warned then
       @@warned = true
       warn msg
    end
  end
end