Accepts_nested_attributes_for 和Belongs_to 多态

我想与建立多态关系accepts_nested_attributes_for。这是代码：

class Contact <ActiveRecord::Base
  has_many :jobs, :as=>:client
end

class Job <ActiveRecord::Base
  belongs_to :client, :polymorphic=>:true
  accepts_nested_attributes_for :client
end

当我尝试访问时Job.create(..., :client_attributes=>{...}给我NameError: uninitialized constant Job::Client

我也遇到了“ArgumentError：无法构建关联 model_name。您是否试图构建多态一对一关联？”的问题。

我找到了解决此类问题的更好方法。您可以使用本机方法。让我们看看 Rails3 中的nested_attributes 实现：

elsif !reject_new_record?(association_name, attributes)
  method = "build_#{association_name}"
  if respond_to?(method)
    send(method, attributes.except(*UNASSIGNABLE_KEYS))
  else
    raise ArgumentError, "Cannot build association #{association_name}. Are you trying to build a polymorphic one-to-one association?"
  end
end

那么实际上我们需要在这里做什么呢？只是在我们的模型中创建 build#{association name} 。我在底部做了完全有效的示例：

class Job <ActiveRecord::Base
  CLIENT_TYPES = %w(Contact)

  attr_accessible :client_type, :client_attributes

  belongs_to :client, :polymorphic => :true

  accepts_nested_attributes_for :client

  protected

  def build_client(params, assignment_options)
    raise "Unknown client_type: #{client_type}" unless CLIENT_TYPES.include?(client_type)
    self.client = client_type.constantize.new(params)
  end
end