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升级到rails3后发现回调中断

ruby-on-rails-3 ruby ruby-on-rails

svilenv · 技术社区 · 14 年前

格雷廷斯!

def self.encode(*attr_names)
  encoder = Encoder.new(attr_names)
  before_save encoder
  after_save encoder            
  after_find encoder
  define_method(:after_find) { } # defining here, since there's only alias in the Encoder class itself            
end

此方法引用编码器类。给你:

class Encoder
  include Encodings 

  def initialize(attrs_to_manage) # We're passed a list of attributes that should be stored encoded in the database
    @attrs_to_manage = attrs_to_manage
  end

  def before_save(model) # Before saving or updating, encode the attributes to their original encoding
    @attrs_to_manage.each do |field|
      model[field] = to_orig_encod(model[field])
    end
  end

  def after_save(model) # After saving, encode them back to utf8
    @attrs_to_manage.each do |field|
      model[field] = to_utf8(model[field])
    end
  end

  alias_method :after_find, :after_save # Do the same after finding an existing record
end

升级到rails3之前,所有回调(保存前、保存后、查找后)都正常工作。升级后 保存前 和 保存后 没有,我在日志中收到以下弃用警告:

DEPRECATION WARNING: Base#after_find has been deprecated, please use Base.after_find :method instead

我不确定如何更改代码以重新启用after\u find回调的功能。我尝试了一些简单的替代方法,但没有成功,关于这个回调的railsapi文档非常有限,而且没有实现的例子。

感谢您的帮助,谢谢!

编辑:

以下是解决方案:

好吧,看来问题比最初看起来更微妙。在额外的测试之后,我发现事实上,正如Jeppe所指出的那样,After\u find回调是有效的,不管是否有弃用警告,“to\u utf8”方法实际上是成功地被调用并在模型属性上执行的。结果与预期不符的原因是“toutf8”方法本身。它使用ruby模块Iconv将字符串从非utf8编码(例如cp1251)转换为utf。这是为使用活动记录从非utf编码的远程遗留数据库中获取的模型属性完成的。然而,事实证明,与以前版本的rails不同,Rails3中的AR 自动并且静默地处理所有对象到ut8的转换,甚至那些从不是unicode的DB获取的对象。所以本质上在升级之后,我的代码最终重新转换成utf8字符串,这些字符串已经被AR转换成utf8,结果是乱七八糟的字符。通过完全删除after\u find和after\u save回调可以解决此问题,因为在本例中不再需要它们:)

1 回复 | 直到 14 年前

Jeppe Liisberg 14 年前

我试图重现您的问题,但我只能重现弃用警告,您可以通过删除

define_method(:after_find) { }

声明。

我的代码:

class Testmodel < ActiveRecord::Base

  def self.encode(*attr_names)
    encoder = Encoder.new(attr_names)
    before_save encoder
    after_save encoder            
    after_find encoder
  end
end

class Encoder
  def initialize(attrs_to_manage) # We're passed a list of attributes that should be stored encoded in the database
    @attrs_to_manage = attrs_to_manage
  end

  def before_save(model) # Before saving or updating, encode the attributes to their original encoding
    @attrs_to_manage.each do |field|
      model[field] = to_orig_encod(model[field])
    end
  end

  def after_save(model) # After saving, encode them back to utf8
    @attrs_to_manage.each do |field|
      model[field] = to_utf8(model[field])
    end
  end

  alias_method :after_find, :after_save # Do the same after finding an existing record

  private
  def to_orig_encod(var)
    "foo"
  end

  def to_utf8(var)
    "bar"
  end
end

控制台测试:

ruby-1.9.2-p0 > Testmodel.create
 => #<Testmodel id: 3, name: nil, created_at: "2010-09-08 14:02:06", updated_at: "2010-09-08 14:02:06"> 
ruby-1.9.2-p0 > Testmodel.last
 => #<Testmodel id: 3, name: nil, created_at: "2010-09-08 14:02:06", updated_at: "2010-09-08 14:02:06"> 
ruby-1.9.2-p0 > Testmodel.encode('name')
 => [Testmodel(id: integer, name: string, created_at: datetime, updated_at: datetime)] 
ruby-1.9.2-p0 > Testmodel.last
 => #<Testmodel id: 3, name: "bar", created_at: "2010-09-08 14:02:06", updated_at: "2010-09-08 14:02:06">

我一直在查阅 http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html 要理解你的问题:-)