Ruby on Rails:子模型的attr_accessor [英] Ruby on Rails: attr_accessor for submodels

问题描述

我正在使用某些模型，其中许多给定模型的关键属性实际上存储在子模型中.

I'm working with some models where a lot of a given model's key attributes are actually stored in a submodel.

示例:

class WikiArticle
  has_many :revisions
  has_one :current_revision, :class_name => "Revision", :order => "created_at DESC"
end
class Revision
  has_one :wiki_article
end

Revision类具有大量的数据库字段，而WikiArticle却很少.但是，我经常必须从WikiArticle的上下文中访问修订版的字段.最重要的情况可能是创建文章.我一直在用很多看起来像这样的方法来做到这一点，每个字段一个:

The Revision class has a ton of database fields, and the WikiArticle has very few. However, I often have to access a Revision's fields from the context of a WikiArticle. The most important case of this is probably on creating an article. I've been doing that with lots of methods that look like this, one for each field:

def description
  if @description
    @description
  elsif current_revision
    current_revision.description
  else
    ""
  end  
end
def description=(string)
  @description = string
end

然后在保存时，我将@description保存到新修订版中.

And then on my save, I save @description into a new revision.

这整个事情让我想起了很多attr_accessor，只是似乎我无法让attr_accessor来做我需要的事情.如何定义attr_submodel_accessor，以便我可以给出字段名称，并像attr_accessor一样自动创建所有这些方法?

This whole thing reminds me a lot of attr_accessor, only it doesn't seem like I can get attr_accessor to do what I need. How can I define an attr_submodel_accessor such that I could just give field names and have it automatically create all those methods the way attr_accessor does?

推荐答案

术语子模型"使我失望，因为它是非标准术语，但我认为您正在寻找的是

The term "submodel" threw me off because it's nonstandard terminology, but I think what you're looking for is delegate. Basically it lets you delegate certain method calls to a property or instance method of an object.

在这种情况下，您将执行以下操作:

In this case you would do something like this:

class WikiArticle
  has_many :revisions
  has_one :current_revision, :class_name => "Revision", :order => "created_at DESC"

  delegate :description, :to => :current_revision
end

您可以根据需要使用多种方法来执行此操作，例如:

You can do this for as many methods as you want, e.g.:

delegate :description, :title, :author, :to => :current_revision

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