Question

我从事有关日程安排的任务，并有类和.yml文件，我想在其中检索数据作为“起点”，“终点”，“价格”等。在我的课堂上，我有方法，我想在其中确定电台是否等于用户选择：

class Train 
  require 'yaml'

  def initialize(time)
    @time = YAML.load_file(time)
  end

  def calc(begin:, end:)
    ary = @time['time']
    start = begin
    stop = end
    res = []
    loop do
      tmp = ary.find { |h| h['begin'] == start }
      break unless tmp
      res << tmp
      start = tmp['end']
      break if start == stop
    end
  end
end

但是它总是在有条件的情况下失败

break unless tmp

例如，如果写入实例变量

a = Train.new("my_path_to yml") 
a.calc(begin: ':washington', end: ':tokyo')

它什么也不执行。即使我重构循环块并编写“ for”迭代器，它也会抛出“ else”条件：

for i in ary
  if i['begin'] == 'washington'
    puts "good"
  else
    puts "no way"
  end
end

这是我的.yml文件

time:
  -
    begin: :washington
    end: :briston
    time: 6
    price: 3
  -
    begin: :briston
    end: :dallas
    time: 4
    price: 2
  -
    begin: :dallas
    end: :tokyo
    time: 3.5
    price: 3
  -
    begin: :tokyo
    end: :chicago
    time: 3.5
    price: 3
  -
    begin: :chicago
    end: :dellawer
    time: 3.5
    price: 3

谢谢！

Answer 1

尝试此更改，检查代码中的注释：

def calc(begin_:, end_:) # <-- don't call variables begin or end, they are reserved words
  ary = @time['time']
  start = begin_
  stop = end_
  res = []
  loop do
    tmp = ary.find { |h| h['begin'] == start }
    break unless tmp
    res << tmp
    start = tmp['end']
    break if start == stop
  end
  res # <-- return something
end

呼叫为：

train.calc(begin_: :washington, end_: :tokyo)
#=> [{"begin"=>:washington, "end"=>:briston, "time"=>6, "price"=>3}, {"begin"=>:briston, "end"=>:dallas, "time"=>4, "price"=>2}, {"begin"=>:dallas, "end"=>:tokyo, "time"=>3.5, "price"=>3}]

请注意不要用符号弄乱字符串。

  ary.each do |i| # for i in ary <-- pythonic! :)
    if i['begin'] == :washington # <-- should be a symbol to pass, not a string
      puts "good"
    else
      puts "no way"
    end
  end

为什么不满足明显条件？

1 个答案: