Ruby-on-rails 如何覆盖 ActiveRecord 模型中的 getter 方法？
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How can I overwrite a getter method in an ActiveRecord model?
提问by oyvindhauge
I'm trying to overwrite a getter method for an ActiveRecord model. I have an attribute called namein the model Category, and I'd like to be able to do something like this:
我正在尝试覆盖 ActiveRecord 模型的 getter 方法。我name在模型中调用了一个属性Category，我希望能够执行以下操作：
def name
name_trans || name
end
If name_transattribute is not nil, then return it, else return nameattribute. How would I do this?
如果name_trans属性不为零，则返回它，否则返回name属性。我该怎么做？
This should then be called normally like this:
然后应该像这样正常调用它：
@category.name
回答by Wonsup Lee
The Rails Style Guiderecommends using self[:attr]over read_attribute(:attr).
在Rails的风格指南建议使用self[:attr]过read_attribute(:attr)。
You can use it like this:
你可以这样使用它：
def name
name_trans || self[:name]
end
回答by meagar
Update: The preferred method according to the Rails Style Guideis to use self[:name]instead of read_attributeand write_attribute. I would encourage you to skip my answer and instead prefer this one.
更新：根据Rails 风格指南的首选方法是使用和self[:name]代替。我鼓励你跳过我的回答，而是更喜欢这个。read_attributewrite_attribute
You can do it exactly like that, except that you need to use read_attributeto actually fetch the value of the name attribute and avoid the recursive call to the namemethod:
您可以完全那样做，只是您需要使用read_attribute来实际获取 name 属性的值并避免对name方法的递归调用：
def name
name_trans || read_attribute(:name)
end
回答by lei liu
I would like to add another option for overwriting getter method, which is simply ：super.
我想再添加一个覆盖getter方法的选项，就是：super。
def name
name_trans || super
end
this works not just on attributes getter method, but also associations getter methods， too。
这不仅适用于属性 getter 方法，也适用于关联 getter 方法。
回答by Patrick Oscity
Overriding the getter and using read_attributedoes not work for associations, but you can use alias_method_chaininstead.
覆盖 getter 和 usingread_attribute对关联不起作用，但您可以alias_method_chain改用。
def name_with_override
name_trans || name_without_override
end
alias_method_chain :name, :override
回答by onemanstartup
If you using store attributes like this
如果您使用这样的商店属性
store :settings, accessors: [:volume_adjustment]
or
using gems like
hstore_accessorgem link
或使用 gems 之类的
hstore_accessorgem 链接
So you ended up using storemethod on model, then to override those method you can't use self.read_attribute, you must use instead superlike that:
所以你最终store在模型上使用了方法，然后要覆盖那些你不能使用的方法self.read_attribute，你必须super像这样使用：
def partner_percentage
super.to_i || 10
end
回答by fangxing
If someone want update the value after name_transin getter method, you could use self[:name]=.
如果有人想name_trans在 getter 方法之后更新值，您可以使用 self[:name]=。
def name
self[:name] = name_trans || self[:name]
# don't do this, it will cause endless loop
# update(name: name_trans)
end
回答by Rajat Bansal
You can use Rails read_attribute method. Rails docs
您可以使用 Rails read_attribute 方法。 Rails 文档
