如何使用Chronic来解析datetime text_field中的日期

Question

我正在尝试获取一个文本字段，我的用户可以在其中输入一些可以被Chronic gem解析的内容。以下是我的模型文件：

require 'chronic'

class Event < ActiveRecord::Base
  belongs_to :user

  validates_presence_of :e_time
  before_validation :parse_date

  def parse_date
    self.e_time = Chronic.parse(self.e_time_before_type_cast) if self.e_time_before_type_cast
  end
end

我认为它之所以被调用，是因为如果我在parse_date中拼错了什么，它就会抱怨它不存在。我也尝试过before_save :parse_date，但也不起作用。

我怎么才能让它工作呢？

谢谢

Answer 1

这种情况看起来很适合使用Event模型中的虚拟属性来表示用于视图目的的自然语言日期和时间，而真正的属性则返回到数据库中。在此screencast中描述了一般技术

所以你的模型中可能有：

class Event < ActiveRecord::Base
  validates_presence_of :e_time

  def chronic_e_time
    self.e_time // Or whatever way you want to represent this
  end

  def chronic_e_time=(s)
    self.e_time = Chronic.parse(s) if s
  end
end

在你看来：

<% form_for @event do |f| %>

  <% f.text_field :chronic_e_time %>

<% end %>

如果解析失败，那么e_time将保持为nil，您的验证将停止保存记录。

Answer 2

我知道现在已经过时了，但我认为这是集成Ruby、Rails和Chronic的最直接的方式。我把this gist放在我的初始化器中：

# https://gist.github.com/eric1234/3739149
#
# Mass monkey-patching! Provides integration between Chronic, Ruby and
# Rails. So now these all work:
#
#     Date.parse "next summer"
#     DateTime.parse "in 3 hours"
#     Time.parse "3 months ago saturday at 5:00 pm"
#
# In addition we override String#to_date, String#to_datetime, String#to_time.
# These methods are used by older version of ActiveRecord when parsing time.
# For newer versions of ActiveRecord, Date::_parse is overridden to also
# use Chronic. This means you can assign a simple string to a ActiveRecord
# attribute:
#
#     my_obj.starts_at = "thursday last week"
#
# Also since the String method are redefined you can easily create dates
# from strings. For example if you want tomorrow at 2pm you can just do:
#
#     'tomorrow at 2pm'.to_time
#
# This is more readable than the following IMHO:
#
#     1.day.from_now.change hour: 14

module Chronic::Extensions
  module String
    def to_date
      parsed = Chronic::Extensions.safe_parse self
      return parsed.to_date if parsed
      super
    end

    def to_datetime
      parsed = Chronic::Extensions.safe_parse self
      return parsed.to_datetime if parsed
      super
    end

    def to_time
      parsed = Chronic::Extensions.safe_parse self
      return parsed.to_time if parsed
      super
    end
  end
  ::String.prepend String

  module DateTime
    def parse datetime, *args
      parsed = Chronic::Extensions.safe_parse datetime
      return parsed.to_datetime if parsed
      super
    end
  end
  ::DateTime.singleton_class.prepend DateTime

  module Date
    def _parse date, *args
      parsed = Chronic::Extensions.safe_parse(date).try :to_datetime
      if parsed
        %i(year mon mday hour min sec sec_fraction offset).inject({}) do |result, fld|
          value = case fld
            when :offset then (parsed.offset * 86400).to_i
            else parsed.public_send fld
          end
          result[fld] = value if value && value != 0
          result
        end
      else
        super
      end
    end

    def parse date, *args
      parsed = Chronic::Extensions.safe_parse date
      return parsed.to_date if parsed
      super
    end
  end
  ::Date.singleton_class.prepend Date

  module Time
    def parse time, now=self.now
      parsed = Chronic::Extensions.safe_parse time, now: now
      return parsed if parsed
      super
    end

    def zone
      super.tap do |cur|
        Chronic.time_class = cur
      end
    end

    def zone= timezone
      super.tap do
        Chronic.time_class = zone
      end
    end
  end
  ::Time.singleton_class.prepend Time

  def self.safe_parse value, options={}
    without_recursion { Chronic.parse value, options }
  end

  # There are cases where Chronic actually uses the Ruby date/time libraries.
  # This leads to infinate recursion as our monkey-patch will intercept the
  # built-in libraries to hand off to Chronic which in turn hands back to the
  # built-in libraries.
  #
  # To avoid this we have this function which acts as a guard to prevent the
  # recursion. If we have already proxied off to Chronic we won't proxy again.
  def self.without_recursion &blk
    unless in_recursion
      self.in_recursion = true
      ret = blk.call
      self.in_recursion = false
    end
    ret
  end
  mattr_accessor :in_recursion
end

Answer 3

基于@bjg所做的工作，您可以在config/initializers/active_record_extend.rb中找到一个有效的解决方案

module ActiveRecord
  class Base
    # Defines natural language getters/setters for date/time fields.
    #
    #   chronic_attr :published_at
    #
    # ...will get you c_published_at & c_published_at=

    def self.chronic_attr(*arguments)
      arguments.each do |arg|

        define_method "c_#{arg}=".to_sym do |dt|
          self[arg] = Chronic::parse(dt)
        end

        define_method "c_#{arg}".to_sym do 
          if self[arg]
            self[arg].to_s(:picker)
          else
            ''
          end
        end
      end
    end
  end
end