如果 - 的 左侧 是 nil，例如departureDate 或 plot 那么你会得到 undefined method '-' for nil:NilClass .In my program Im getting an error which says ./ruby_camping.rb:91:in `-': nil can't be coerced into Fixnum (TypeError). What I would like to do is to checkout a guest that I have just checked in. Here is the block of code for the checkout part:def self.check_out puts "Welcome to checkout!" puts $camping.current_guests puts " Here are the current guests, who do you want to checkout?!" puts "State plot number " plot = gets.chomp.to_i guest = $camping.current_guests[plot-1] puts "State the date for your checkout (a number bigger then " + guest.arrived.to_s + "): " # it should not be possible for a guest to checkout before she has checked in departureDate = gets.chomp.to_i guestStayedDays = departureDate - guest.arrived #Days the guest has stayed while (guestStayedDays < 1) do puts "The date for checkout is not valid. The guest checked in " + guest.arrived.to_s puts "Please state a new date." departureDate = gets.chomp.to_i guestStayedDays = departureDate - guest.arrived end guest.departure = departureDate guest.plot.increase(guestStayedDays) # increases the electricity meter puts guest # prints the guest $camping.current_guests[plot-1] = nil # emptys the plot endendHow come departureDate still is nil? Thankful for help! 解决方案 To get a more detailed answer, you would have to indicate which line was line 91 in your program. However to point you in the right direction, if you're seeing nil can't be coerced into Fixnum then it means something on the right hand side of a - is nil. e.g.irb(main):001:0> 5 - nilTypeError: nil can't be coerced into Fixnum from (irb):1:in `-' from (irb):1From your code the only possible example of this I can see is guestStayedDays = departureDate - guest.arrived so I would check the value of guest.arrived.If something on the left hand side of a - were nil e.g. departureDate or plot then you would get undefined method '-' for nil:NilClass instead. 这篇关于`-': nil 不能被强制转换为 Fixnum (TypeError)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！
