Ruby - 失败语句/保护条件返回 nil

Question

我正在尝试改进release_bike方法。我已经进入了 irb，第一个保护条件有效，release_working_bikes工作，但第二个保护条件在 irb 中保持返回 nil，即使我运行功能测试并且知道只有一辆坏掉的自行车可用。

我措辞第二

条失败线的方式有问题，还是broken_bikes有缺陷？

release_bike方法应按如下方式工作;如果扩展坞中没有自行车，那么应该有一个警告说 - No bikes available如果扩展坞中有自行车，但它们都坏了，那么应该有一个警告说 - No working bikes available如果有一些工作自行车，那么release_bike应该释放其中一辆工作自行车。

以下是涉及的两个类;

require_relative 'bike'
class DockingStation
  DEFAULT_CAPACITY = 20
  attr_reader :capacity, :bikes
  def initialize(capacity = DEFAULT_CAPACITY)
    @bikes = []
    @capacity = capacity
  end
  def release_bike
    fail 'No bikes available' if empty?
    fail 'No working bikes available' unless broken_bikes
    release_working_bikes
  end
  def dock(bike)
    fail 'Docking Station Full' if full?
    @bikes << bike
  end
  private
  def working_bikes
    @bikes.each { |bike| return bike unless bike.broken? }
  end
  def broken_bikes
    not_working = []
    not_working << @bikes.each { |bike| return bike if bike.broken? }
    not_working.empty?
  end
  def release_working_bikes
    bike = working_bikes
    @bikes.delete(bike)
  end
  def full?
    @bikes.count >= @capacity
  end
  def empty?
    @bikes.empty?
  end
end

class Bike
  attr_accessor :broken
  def initialize
    @broken = false
  end
  def working?
    @working
  end
  def report_broken
    @broken = true
  end
  def broken?
    @broken
  end
end

Answer 1

正如评论中已经指出的那样，您正在尝试检查是否所有自行车都坏了，那么为什么不将您的方法命名为 all_bikes_broken? .请参阅代码中的注释。

require_relative 'bike'
class DockingStation
  DEFAULT_CAPACITY = 20
  attr_reader :capacity, :bikes
  def initialize(capacity = DEFAULT_CAPACITY)
    @bikes = []
    @capacity = capacity
  end
  def release_bike
    fail 'No bikes available' if empty?
    fail 'No working bikes available' unless all_bikes_broken?
    release_working_bikes
  end
  def dock(bike)
    fail 'Docking Station Full' if full?
    @bikes << bike
  end
  private
  def working_bikes
    #this will select only bikes which are NOT broken
    @bikes.reject{ |bike| bike.broken? }
  end
  def all_bikes_broken?
    #this is shorthand for @bikes.all?{ |bike| bike.broken? }
    #it says send  :broken? method to each instance of bike.
    #.all? returns true only if all instances return true, otherwise false.
    @bikes.all?(&:broken?)
  end
  def release_working_bikes
    bike = working_bikes
    @bikes.delete(working_bikes.first)
    #or you could do .last but order probably doesn't matter here.
  end
  def full?
    @bikes.count >= @capacity
  end
  def empty?
    @bikes.empty?
  end
end

class Bike
  attr_accessor :broken
  def initialize
    @broken = false
  end
  def working?
    @working
  end
  def report_broken
    @broken = true
  end
  def broken?
    @broken
  end
end