ruby-on-rails - 干掉范围？

Question

这里是 ruby 初学者。我定义了以下范围，我有一种强烈的感觉，我可以用更干燥的方式来做到这一点。关于如何以较少重复的方式执行此操作有什么想法吗？

scope :end_during, ->(new_start_time, new_end_time) do
  if (!new_start_time.nil?) && (!new_end_time.nil?)
    where('end_time > ? AND end_time < ?', new_start_time, new_end_time)
  else
    return nil
  end
end

scope :start_during, ->(new_start_time, new_end_time) do
  if (!new_start_time.nil?) && (!new_end_time.nil?)
    where('start_time > ? AND start_time < ?', new_start_time, new_end_time)
  else
    return nil
  end
end

scope :happening_during, ->(new_start_time, new_end_time) do
  if (!new_start_time.nil?) && (!new_end_time.nil?)
    where('start_time > ? AND end_time < ?', new_start_time, new_end_time)
  else
    return nil
  end 
end

scope :enveloping, ->(new_start_time, new_end_time) do
  if (!new_start_time.nil?) && (!new_end_time.nil?)
    where('start_time < ? AND end_time > ?', new_start_time, new_end_time)
  else
    return nil
  end
end

scope :identical, ->(new_start_time, new_end_time) do
  if (!new_start_time.nil?) && (!new_end_time.nil?)
    where('start_time = ? AND end_time = ?', new_start_time, new_end_time)
  else
    return nil
  end
end

它们是这样使用的:

def overlaps
  overlapping_bookings = [ 
    subject.bookings.end_during(start_time, end_time),
    subject.bookings.start_during(start_time, end_time),
    subject.bookings.happening_during(start_time, end_time),
    subject.bookings.enveloping(start_time, end_time),
    subject.bookings.identical(start_time, end_time)
  ].flatten

 overlapping_bookings.delete self
 if overlapping_bookings.any?
   errors.add(:base, 'Slot has already been booked')
 end
end

Answer 1

您可以将通用的东西分解到另一个作用域中，然后从您的各个作用域中使用正确的参数调用它:

scope :time_constraint, ->(c1, f1, c2, f2) do
  return nil unless f1 && f2
  where "%s ? AND %s ?" % [c1, c2], f1, f2
end

scope :end_during,       ->(start_time, end_time) { time_constraint "end_time >",   start_time, "end_time <",   end_time }
scope :start_during,     ->(start_time, end_time) { time_constraint "start_time >", start_time, "start_time <", end_time }
scope :happening_during, ->(start_time, end_time) { time_constraint "start_time >", start_time, "end_time <",   end_time }
scope :enveloping,       ->(start_time, end_time) { time_constraint "start_time <", start_time, "end_time >",   end_time }
scope :enveloping,       ->(start_time, end_time) { time_constraint "start_time =", start_time, "end_time =",   end_time }

它读起来也不错。