覆盖默认访问器时更新属性时出现问题 [英] Trouble on updating attributes when default accessors are overwritten

问题描述

我正在使用Ruby on Rails 4，并且已经以这种方式覆盖了一些默认的访问器方法:

I am using Ruby on Rails 4 and I have overwritten some default accessor method this way:

class Article < ActiveRecord::Base
  def title
    self.get_title
  end

  def content
    self.get_content
  end
end

self.get_title和self.get_content方法返回一些计算值，如下所示(注意:has_one_association是:has_one ActiveRecord::Association)

self.get_title and self.get_content methods return some computed value and look like the following (note: has_one_association is a :has_one ActiveRecord::Association)

def get_title
  self.has_one_association.title.presence || read_attribute(:title)
end

def get_content
  self.has_one_association.content.presence || read_attribute(:content)
end

当我从数据库中找到并读取@article实例时，所有实例均按预期工作:title和content值分别通过self.has_one_association.title和self.has_one_association.content输出.

When I find and read @article instances from the database all works as expected: title and content values are respectively outputted with self.has_one_association.title and self.has_one_association.content.

但是，我发现，当将属性分配给@article时，@article对象将得到 not 的预期更新.也就是说，在我的控制器中，我有:

However, I found that when attributes are assigned to an @article then the @article object is not updated as expected. That is, given in my controller I have:

def update
  # params # => {:article => {:title => "New title", :content => "New content"})}

  ...

  # BEFORE UPDATING
  # @article.title   # => "Old title"   # Note: "Old title" come from the 'get_title' method since the 'title' accessor implementation
  # @article.content # => "Old content" # Note: "Old content" come from the 'get_content' method since the 'content' accessor implementation

  if @article.update_attributes(article_params)

    # AFTER UPDATING
    # @article.title   # => "Old title"
    # @article.content # => "Old content"

    ...
  end
end

def article_params
  params.require(:article).permit(:title, :content)
end

即使@article有效，它也没有在数据库中更新(！)，我认为这是因为我覆盖访问器的方式和/或Rails assign_attributes的方式.当然，如果我删除了getter方法，那么所有方法都会按预期工作.

Even if the @article is valid it has not been updated in the database (!), I think because the way I overwrite accessors and/or the way Rails would assign_attributes. Of course, if I remove the getter methods then all works as expected.

这是一个错误吗?我该如何解决这个问题?或者，我应该采用另一种方法来完成我想完成的工作吗?

Is it a bug? How can I solve the problem? Or, should I adopt another approach in order to make what I would like to accomplish?

另请参见 https://github.com/rails/rails/issues/14307

推荐答案

update_attributes只是调用title=，content=和save的快捷方式.如果您不覆盖设置器，仅覆盖获取器，则不相关.

update_attributes in this case is just a shortcut for calling title=, content=, and save. If you're not overwriting the setters, just the getters, it is not related.

您正在正确更新值，但是Rails不会读取您正在设置的值，这是因为覆盖了要从关联中读取的getter.您可以通过检查@article.attributes或查看数据库中的文章记录来验证这一点.

You're updating the values correctly, but Rails isn't reading the values you're setting, due to overwriting the getters to read from the association instead. You could verify this by checking @article.attributes, or looking at the article record in the database.

此外，您的get_content尝试使用read_attribute(:title)而不是:content.

Also, your get_content is trying to read_attribute(:title) instead of :content.

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