Question

The code below helps calculate business hours for completing tasks. In the calculate_deadline method, in the BusinesHours Class, the two puts statements reveal this

 puts self
#<BusinessHours:0x000001008cbb70>

  puts self[start_time.to_date].inspect
#<TimeRange:0x000001008cbb48 @range=2010-06-10 09:00:00 -0700..2010-06-10 15:00:00 -0700>

I don’t understand why putting start_time.to_date beside ‘self’ in calculate_deadline changes self from BusinessHours class to TimeRange class, as the two puts statements suggest, especially since the ‘to_date’ method is part of class Time. Can you explain how this is happening?

require 'time'
require 'date'

class Time
  def to_date
    Date.new(year, month, day)
  end
end

class BusinessHours

  def initialize(time_in, time_out)
    @default_range = TimeRange.new(time_in, time_out)
    @modified_days = {}
  end

  def update(day, time_in, time_out)
    key = day.is_a?(Symbol) ? day : Date.parse(day)
    @modified_days.merge!({key => TimeRange.new(time_in, time_out)})
  end

  def closed(*days)
    days.each {|day| update(day, '0:00', '0:00')}      
  end

  def [](date)
    day_of_week = date.strftime("%a").downcase.to_sym
    range = @modified_days[date] || @modified_days[day_of_week] || @default_range
    # reset time range dates to match date param
    range.reset_date(date)
    range
  end

  def calculate_deadline(seconds, start_time)
    start_time = Time.parse(start_time)
    puts self
    puts self[start_time.to_date].inspect
    range = self[start_time.to_date]


    if range.applies?(start_time)
      start_time = [start_time, range.start].max
      available_seconds = range.stop - start_time

      return start_time + seconds if available_seconds > seconds
      seconds -= available_seconds
    end

    calculate_deadline(seconds, (start_time.to_date + 1).to_s)
  end

end

class TimeRange

  def initialize(time_in, time_out)
    @range = Time.parse(time_in)..Time.parse(time_out)

  end

  def reset_date(date)
    @range = Time.local(date.year, date.month, date.day, start.hour, start.min)..
      Time.local(date.year, date.month, date.day, stop.hour, stop.min)    
  end

  def applies?(time)
    stop > time
  end

  def stop

    @range.end
  end

  def start
    @range.begin
  end

end

k = BusinessHours.new("9:00 AM", "3:00 PM")
k.calculate_deadline(20*60*60, "Jun 7, 2010 10:45 AM")

Answer 1

@default_range = TimeRange.new(time_in, time_out)

From that line, we can see that @default_range is a TimeRange instance, and that @modified_days is an empty hash (therefore @modified_days[anything] will be nil, i.e. falsey).

range = @modified_days[date] || @modified_days[day_of_week] || @default_range

Since @modified_days[anything] is falsey, range ends up being @default_range, which, as we see above, is a TimeRange object. Your [] method on BusinessHours returns the range variable, which is a TimeRange object.

Therefore, with self being a BusinessHours object, when you call the [] method (self[argument]), you will get a TimeRange object.