ActiveRecord的::商店使用默认值

本文介绍了ActiveRecord的::商店使用默认值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

使用新的ActiveRecord ::商店系列化，的文档给出如下示例实现：

Using the new ActiveRecord::Store for serialization, the docs give the following example implementation:

class User < ActiveRecord::Base
  store :settings, accessors: [ :color, :homepage ]
end

是否有可能使用默认值来声明属性，一个类似于：

Is it possible to declare attributes with default values, something akin to:

store :settings, accessors: { color: 'blue', homepage: 'rubyonrails.org' }

推荐答案

没有，有没有办法来提供存储调用中的默认值。该<$c$c>store宏是相当简单：

No, there's no way to supply defaults inside the store call. The store macro is quite simple:

def store(store_attribute, options = {})
  serialize store_attribute, Hash
  store_accessor(store_attribute, options[:accessors]) if options.has_key? :accessors
end

和所有的 store_accessor 并通过迭代：访问和创建存取和突变的方法为每一个。如果您尝试使用哈希与：访问你最终会加入一些东西到你的存储你没T意思。

And all store_accessor does is iterate through the :accessors and create accessor and mutator methods for each one. If you try to use a Hash with :accessors you'll end up adding some things to your store that you didn't mean to.

如果你要提供的默认值，那么你可以使用 after_initialize 挂钩：

If you want to supply defaults then you could use an after_initialize hook:

class User < ActiveRecord::Base
  store :settings, accessors: [ :color, :homepage ]
  after_initialize :initialize_defaults, :if => :new_record?
private
  def initialize_defaults
    self.color    = 'blue'            unless(color_changed?)
    self.homepage = 'rubyonrails.org' unless(homepage_changed?)
  end
end

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Accessors