Rails验证虚拟属性，设置表单错误。 Railscast＃32

class Task < ActiveRecord::Base

attr_accessible :description, :complete, :deadline

validate :deadline_string_no_errors


def deadline_string
  self.deadline.to_s
end

def deadline_string=(deadline_str)
  unless deadline_str.blank?
    begin
      self.deadline = Chronic.parse(deadline_str)
    rescue
      self.deadline = Time.parse(deadline_str)
    rescue
      @deadline_invalid = true
    end
  end
end

def deadline_string_no_errors
  errors.add(:deadline_string, \"Is Invalid\") if @deadline_invalid
end

Chronic.parse(\'2011-05-25 08:19:00 UTC\')

deadline_string=\"foobar\"

# snip
def deadline_string=(deadline_str)
  unless deadline_str.blank?
    self.deadline = ( parse_time(deadline_str, Chronic) || parse_time(deadline_str, Time) )
  end
end

private

def parse_time(string, parser)
  begin
    parser.parse(string)
  rescue
    @deadline_invalid = true
  end
end

def deadline_string_no_errors
  #snip
end

self.deadline

Class Task < ActiveRecord::Base
  attr_accessible: description, :complete, :deadline

  validate :deadline_string_no_errors

  def deadline_string
    self.deadline.to_s
  end

  def deadline_string=(deadline_str)
    unless deadline_str.blank?
      self.deadline = ( parse_time(deadline_str, Chronic) || parse_time(deadline_str, Time) )
      @deadline_invalid = true if self.deadline.nil?
    end
  end

  private

  def parse_time(string, parser)
    begin
      parser.parse(string)
    rescue
    end
  end

  def deadline_string_no_errors
    errors.add(:deadline_string, \"Is Invalid\") if @deadline_invalid
  end