Question

我想知道为什么while循环中的IF语句只会触发一次。 我应该获得4个连接的行，但我只是得到2个。 显然，IF没有正常发射

我基本上想要列出给定列车编号的下一个时刻表（time_tables）。

谢谢！

require 'date'

Time_tables =   [
    { name: '01251', start_date: '2014-04-24 22:03:00', start_location: 'A', end_date: '2014-04-24 22:10:00', end_location: 'BC' },
    { name: '05012', start_date: '2014-04-24 22:20:00', start_location: 'RI', end_date: '2014-04-24 23:10:00', end_location: 'XX' },
    { name: '03232', start_date: '2014-04-24 17:10:00', start_location: 'X', end_date: '2014-04-24 20:10:00', end_location: 'B' },
    { name: '02435', start_date: '2014-04-24 17:10:00', start_location: 'Z', end_date: '2014-04-24 20:10:00', end_location: 'B' },
    { name: '04545', start_date: '2014-04-24 22:15:00', start_location: 'BC', end_date: '2014-04-24 22:20:00', end_location: 'RI' },
    { name: '03545', start_date: '2014-04-24 23:15:00', start_location: 'XX', end_date: '2014-04-25 00:10:00', end_location: 'E' }
]

class TrainSearch
  def initialize(data)
    @data = data
  end

  def rows
    @rows ||= @data.map {|row| Row.new(row)}
  end

  # { name: '01251', start_date: '2014-04-24 22:03:00', start_location: 'A', end_date: '2014-04-24 22:10:00', end_location: 'BC' }
  def find_train(train_number)
    rows.find { |row| row.name == train_number }
  end


  def find_next_route(after_time, end_location)
    rows.find { |row| row.start_date > after_time and row.start_location == end_location }
  end

  def find_train_and_next_routes(train_number)
    if find_train(train_number)
      train = find_train(train_number)
      routes = [train] # add the train as the first route
    else
      p 'not valid number'
    end
    # we search first to see if we find a route
    # we reassign the train variable to the new train found
    #if(train = find_next_route(train.end_date, train.end_location))
    i = 0
    while i <= rows.count  do
      if(train = find_next_route(routes[-1].end_date, routes[-1].end_location))
        p 'are we in ?: '
        p i
        routes << train
      end
    i += 1
    end
    # at the end return the train and the routes
    return routes

  end



  # Do this because we need to parse the date into a time to sort
  class Row
    def initialize(row)
      @row = row
    end

    def start_date
      DateTime.parse(@row[:start_date])
    end

    def end_date
      DateTime.parse(@row[:end_date])
    end

    def name
      @row[:name]
    end

    def start_location
      @row[:start_location]
    end

    def end_location
      @row[:end_location]
    end
  end
end

user = TrainSearch.new(Time_tables)
p user.find_train_and_next_routes '01251'

Answer 1

为什么你期待4条路线？我假设你想要这个

#=> [
  #<TrainSearch::Row:0x26f3c58 @row={:name=>"01251", :start_date=>"2014-04-24 22:03:00",:start_location=>"A", :end_date=>"2014-04-24 22:10:00", :end_location=>"BC"}>,
  #<TrainSearch::Row:0x26f3bf8 @row={:name=>"04545", :start_date=>"2014-04-24 22:15:00", :start_location=>"BC", :end_date=>"2014-04-24 22:20:00", :end_location=>"RI"}>, 
  #<TrainSearch::Row:0x26f3c40 @row={:name=>"05012", :start_date=>"2014-04-24 22:20:00", :start_location=>"RI", :end_date=>"2014-04-24 23:10:00", :end_location=>"XX"}>,
  #<TrainSearch::Row:0x26f3be0 @row={:name=>"03545", :start_date=>"2014-04-24 23:15:00",:start_location=>"XX", :end_date=>"2014-04-25 00:10:00", :end_location=>"E"}>]

如果是这样，你的问题是那个

#<TrainSearch::Row:0x26f3c40 @row={:name=>"05012", :start_date=>"2014-04-24 22:20:00", :start_location=>"RI", :end_date=>"2014-04-24 23:10:00", :end_location=>"XX"}>

与

的end_date同时开始

#<TrainSearch::Row:0x26f3bf8 @row={:name=>"04545", :start_date=>"2014-04-24 22:15:00", :start_location=>"BC", :end_date=>"2014-04-24 22:20:00", :end_location=>"RI"}>

因此

def find_next_route(after_time, end_location) rows.find { |row| row.start_date > after_time && row.start_location == end_location } end

返回nil，因为row.start_date > after_time为false，添加>=会获得所需的结果

您也可以按如下方式实施Row

class Row
  attr_reader :row,:start_date,:end_date,:name,:start_location,:end_location
  def initialize(row)
    @row = row
    @row.each &method(:instance_variable_set)
  end
end

IF循环中的IF语句不起作用

1 个答案: