Ruby-on-rails 覆盖 ActiveRecord 属性方法
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Override ActiveRecord attribute methods
提问by Aaron Longwell
An example of what I'm talking about:
我正在谈论的一个例子：
class Person < ActiveRecord::Base
def name=(name)
super(name.capitalize)
end
def name
super().downcase # not sure why you'd do this; this is just an example
end
end
This seems to work, but I was just read the section on overriding attribute methods in the ActiveRecord::Base docs, and it suggests using the read_attributeand write_attributemethods. I thought there must be something wrong with what I'm doing in the example above; otherwise, why would they bless these methods as the "right way" to override attribute methods? They're also forcing a much uglier idiom, so there must be a good reason...
这似乎有效，但我刚刚阅读了ActiveRecord::Base docs 中关于覆盖属性方法的部分，它建议使用read_attribute和write_attribute方法。我认为我在上面的例子中所做的一定有问题；否则，为什么他们会祝福这些方法是覆盖属性方法的“正确方法”？他们还强迫使用更丑陋的习语，所以一定有一个很好的理由......
My real question: Is there something wrong with this example?
我真正的问题是：这个例子有什么问题吗？
回答by Aaron Longwell
Echoing Gareth's comments... your code will not work as written. It should be rewritten this way:
回应 Gareth 的评论……您的代码将无法正常工作。应该这样改写：
def name=(name)
write_attribute(:name, name.capitalize)
end
def name
read_attribute(:name).downcase # No test for nil?
end
回答by mipadi
As an extension to Aaron Longwell's answer, you can also use a "hash notation" to access attributes that have overridden accessors and mutators:
作为 Aaron Longwell 答案的扩展，您还可以使用“哈希符号”来访问已覆盖访问器和修改器的属性：
def name=(name)
self[:name] = name.capitalize
end
def name
self[:name].downcase
end
回答by jcnnghm
There is some great information available on this topic at http://errtheblog.com/posts/18-accessor-missing.
http://errtheblog.com/posts/18-accessor-missing上有一些关于此主题的重要信息。
The long and short of it is that ActiveRecord does correctly handle super calls for ActiveRecord attribute accessors.
总而言之，ActiveRecord 确实正确处理了对 ActiveRecord 属性访问器的超级调用。
回答by chriseppstein
I have a rails plugin that makes attribute overriding work with super as you would expect. You can find it on github.
我有一个 rails 插件，它使属性覆盖与您期望的 super 一起使用。你可以在github上找到它。
To install:
安装：
./script/plugin install git://github.com/chriseppstein/has_overrides.git
To use:
使用：
class Post < ActiveRecord::Base
has_overrides
module Overrides
# put your getter and setter overrides in this module.
def title=(t)
super(t.titleize)
end
end
end
Once you've done that things just work:
一旦你完成了这些事情就可以了：
$ ./script/console
Loading development environment (Rails 2.3.2)
>> post = Post.new(:title => "a simple title")
=> #<Post id: nil, title: "A Simple Title", body: nil, created_at: nil, updated_at: nil>
>> post.title = "another simple title"
=> "another simple title"
>> post.title
=> "Another Simple Title"
>> post.update_attributes(:title => "updated title")
=> true
>> post.title
=> "Updated Title"
>> post.update_attribute(:title, "singly updated title")
=> true
>> post.title
=> "Singly Updated Title"
