好了，伙计们，这是一个在终端上运行的地下城文本冒险项目。
当用户说他想“北上”时，它会分割字符串：第一个单词检查方法，第二个单词检查参数发生在其他地方，我复制粘贴了两个方法，这两个方法给了我以下问题：
当它调用go（north）并且north不是有效连接时，它会显示选项并再次询问用户方向，此时用户输入的输入由于某种原因存储为Nil。
为什么？？我也试过STDIN.gets.chomp.downcase结果也是一样
代码如下：
def find_room_in_direction(direction)
##-> if room connects with other on that direction, returns connection
if find_room_in_dungeon(@player.location).connections.include?(direction.to_sym)
return find_room_in_dungeon(@player.location).connections[direction.to_sym]
##-> if direction connection is not found,
##-> show possible connections & return trigger to ask again inside go()
elsif !find_room_in_dungeon(@player.location).connections.include?(direction.to_sym)
puts "I don't see any #{direction}..."
puts "This room only connects #{(find_room_in_dungeon(@player.location)).connections.keys.join(', ')}"
puts "Where should we go?"
return :redo
end
end
def go(direction)
current_direction = @player.location
new_direction = find_room_in_direction(direction)
##-> if REDO trigger received, ask for new direction & try again
if new_direction == :redo
puts "REDOING DIRECTION"
##-> HERE IS THE PROBLEM:
##-> this does ask for input
new_direction = gets.chomp.downcase!
##-> but it saves Nil instead of the input, so that puts shows ''
puts "#{new_direction}"
##-> so this call trows an error: cant call method to Nil
new_direction = find_room_in_direction(new_direction)
##-> if user entered valid direction from start, the following would run
elsif new_direction != :redo && current_direction != new_direction
@player.location = new_direction
puts "You go #{direction},"
puts "and enter #{show_current_description}"
end
end
有什么建议吗？
谢谢！
最佳答案
您使用的是downcase!而不是downcase。downcase!就地更改字符串，如果没有更改，则返回nil（这就是这里发生的情况）。
str = "teSt"
puts str.downcase # test
puts str # teSt
str.downcase!
puts str # test
见the documentation for
downcase!