如何初始化“attr_accessor中”属性值？ [英] How to initialize 'attr_accessor' attribute values?

问题描述

可能重复：结果
   attr_accessor中的默认值

我on Rails的3.0.9使用Ruby，我想初始化一些 attr_accessor中中从 ActiveRecord的继承我的类\\型号属性值:: Base的。即，

I am using Ruby on Rails 3.0.9 and I would like to initialize some attr_accessor attribute values in my class\model that inherits from ActiveRecord::Base. That is,

...我的模块中我有：

... in my module I have:

class User < ActiveRecord::Base
  attr_accessor :attribute_name1,
                :attribute_name2,
                :attribute_name3,
                ...
end

和我想设置为真正所有 attr_accessor中属性值的。 我怎么能这样做？

的 P.S：的我当然想解决逼近点菜Ruby on Rails的路上面的问题。我知道关于 after_initialize 回调，但使用这种方法，我应该重复每个 ATTRIBUTE_NAME＆LT; N＆GT; 语句，我会喜欢将值设置为真正的 after_initialize 语句（...和这里面是的不干 - 不要重复自己）。也许有更好的方式来实现这一目标。的有没有一种方法来设置 attr_accessor中当你说出这些属性对飞属性值？也就是说，我希望宣布和设置 attr_accessor中属性一次！的

P.S.: Of course I would like to solve the above issue approaching "à la Ruby on Rails Way". I know about the after_initialize callback but by using that method I should repeat each attribute_name<N> statement for which I would like to set the value to true inside that after_initialize statement (... and this is not DRY - Don't Repeat Yourself). Maybe there is a better way to achieve this. Is there a way to set attr_accessor attribute values "on the fly" when you state those attributes? That is, I expect to declare and set attr_accessor attributes at once!

推荐答案

有关的Rails 3.2或更早版本，你可以使用的 attr_accessor_with_default ：

For Rails 3.2 or earlier, you could use attr_accessor_with_default:

class User < ActiveRecord::Base
  attr_accessor_with_default :attribute_name1, true
  attr_accessor_with_default :attribute_name2, true
  attr_accessor_with_default :attribute_name3, true
  ...
end

由于您的默认值是一个不可变的类型（布尔），这种形式的方法是安全的，在这里使用。但是，如果默认值是一个可变对象，包括数组或字符串不使用它，因为所有新的模型对象将共享完全相同的情况下，这可能不是你想要的。

Since your default value is an immutable type (boolean), this form of the method is safe to use here. But don't use it if the default value is a mutable object, including an array or string, because all of your new model objects will share the exact same instance, which is probably not what you want.

相反， attr_accessor_with_default 将接受块，在那里你可以每次都返回一个新的实例：

Instead, attr_accessor_with_default will accept a block, where you can return a new instance each time:

attr_accessor_with_default(:attribute_name) { FizzBuzz.new }

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