Ruby on rails 更新父项时未设置父项id

我有两种型号

class Parent < ActiveRecord::Base
  has_one :child
  accepts_nested_attributes_for_child :child
end

当我在自定义\u验证中检查父\u id时，它会返回我nil，并为parent.attribute\u one获取nil类错误，因为parent为nil我在这里做错了什么。 这是回溯

NoMethodError (undefined method `attribute_one' for nil:NilClass):
  app/models/child.rb:8:in `custom_validation'
  app/controllers/parents_controller.rb:12:in `update'


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  Rendered vendor/bundle/ruby/2.2.0/gems/web-console-2.1.1/lib/web_console/templates/style.css within layouts/inlined_string (0.5ms)
  Rendered vendor/bundle/ruby/2.2.0/gems/web-console-2.1.1/lib/web_console/templates/_inner_console_markup.html within layouts/inlined_string (0.4ms)
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---

这是一个愚蠢的错误，我忘了为child在强参数中添加id

def trasnfer_params
  params.require(:parent).permit(:attribute_one, :attribute_two, child_attributes:[:id, :parent_id, :attribute_one]) #added id in child_attributes
end

---

已解决。

如果self.attribute\u one>self.parent.attribute\u one我尝试了self.parent或parent将返回nil，除非未设置parent\u id。请在此处使用并发布异常堆栈跟踪。我们必须以某种方式检查记录保存是否成功。@mudasobwa我已经更新了这个问题

NoMethodError (undefined method `attribute_one' for nil:NilClass):
  app/models/child.rb:8:in `custom_validation'
  app/controllers/parents_controller.rb:12:in `update'


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  Rendered vendor/bundle/ruby/2.2.0/gems/actionpack-4.2.0/lib/action_dispatch/middleware/templates/rescues/diagnostics.text.erb (19.6ms)
  Rendered vendor/bundle/ruby/2.2.0/gems/web-console-2.1.1/lib/web_console/templates/_markup.html (0.4ms)
  Rendered vendor/bundle/ruby/2.2.0/gems/web-console-2.1.1/lib/web_console/templates/style.css within layouts/inlined_string (0.5ms)
  Rendered vendor/bundle/ruby/2.2.0/gems/web-console-2.1.1/lib/web_console/templates/_inner_console_markup.html within layouts/inlined_string (0.4ms)
  Rendered vendor/bundle/ruby/2.2.0/gems/web-console-2.1.1/lib/web_console/templates/_prompt_box_markup.html within layouts/inlined_string (0.3ms)
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  Rendered vendor/bundle/ruby/2.2.0/gems/web-console-2.1.1/lib/web_console/templates/index.html (34.4ms)

def trasnfer_params
  params.require(:parent).permit(:attribute_one, :attribute_two, child_attributes:[:id, :parent_id, :attribute_one]) #added id in child_attributes
end