Ruby on Rails 3 - 序列化数组不匹配的类挡板答案

【问题标题】：Ruby on Rails 3 - Serialize Array Mismatched Class BafflementRuby on Rails 3 - 序列化数组不匹配的类挡板
【发布时间】：2011-07-06 15:03:18
【问题描述】：

你好，我对 Rails 3.0.5 和 Ruby 1.9.2 中的序列化不匹配问题感到困惑。我正在使用 Array 的子类为数据库播种，然后尝试保存到 ActiveRecord 对象。谁能帮帮我吗？我最初试图序列化为 Graph 但将其减少为 Array 以避免自定义类的错误。我很困惑，因为这对我来说没有直观的意义。非常感谢您的帮助！

class Graph < Array
  ..

class Settings < ActiveRecord::Base
  serialize :graphs, Array
  ..

seeds.rb 中的最后几行——例如之后什么都没有发生。只是为了调试目的节省了很多：

  sh_1g = sh_1g.to_a
  d.company.settings.add_graph(sh_1g.to_a)
  d.company.settings.save!
  d.company.save!  
  d.save!
  if sh_1g == d.company.settings.graphs[0]
    puts "the added graph matches the first graph in the graphs array"
  end
  puts "added " + sh_1g.inspect + " to " + d.company.settings.graphs.inspect
  puts "class of added graph as saved is" + d.company.settings.graphs[0].class.inspect
  puts "class of added graph is " + sh_1g.class.inspect
  puts "class of graphs serial is " + d.company.settings.graphs.class.inspect

seeds.rb 运行时的输出：

the added graph matches the first graph in the graphs array
added [[[0, 0, ..]]] to to [[[[0, 0, ..]]]..]
class of added graph as saved isArray
class of added graph is Array
class of graphs serial is Array

但是，在控制台中：

ruby-1.9.2-p180 :002 > Company.all[1].settings
ActiveRecord::SerializationTypeMismatch: graphs was supposed to be a Array, but was a String
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.5/lib/active_record/attribute_methods/read.rb:106:in `unserialize_attribute'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.5/lib/active_record/attribute_methods/read.rb:82:in `read_attribute'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.5/lib/active_record/base.rb:1586:in `attribute_for_inspect'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.5/lib/active_record/base.rb:1667:in `block in inspect'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.5/lib/active_record/base.rb:1665:in `collect'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.5/lib/active_record/base.rb:1665:in `inspect'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.5/lib/active_record/associations/association_proxy.rb:146:in `inspect'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.5/lib/rails/commands/console.rb:44:in `start'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.5/lib/rails/commands/console.rb:8:in `start'
    from /Users/dlipa/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.5/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

【问题讨论】：

奇怪的观察——如果我从控制台运行这段代码没有问题。

标签： ruby-on-rails ruby-on-rails-3 serialization activerecord

【解决方案1】：

我遇到了与此类似的问题。我的问题源于我的serialize :some_column, Array 声明的放置。如果在调用 serialize 之前定义了 ActiveRecord 对象类上的属性方法，那么您将无法正确定义 setter 和 getter 方法。

所以，在您声明哪些列被序列化之前，我会确保不会在您的 Settings 类上调用 define_attribute_methods。

【讨论】：

【解决方案2】：

设置选项

:null => true

在“图表”字段的迁移中。它修复了这个错误

【讨论】：