在class_eval中使用super [英] Using super with class_eval

问题描述

我有一个应用程序，该模块在核心类中包含用于添加客户端自定义项的模块.

I have an app that includes modules into core Classes for adding client customizations.

我发现class_eval是重写核心Class中的方法的好方法，但是有时候我想避免重写整个方法，而只是遵循原始方法.

I'm finding that class_eval is a good way to override methods in the core Class, but sometimes I would like to avoid re-writing the entire method, and just defer to the original method.

例如，如果我有一个名为account_balance的方法，那么最好在我的模块(即包含在Class中的模块)中做类似的事情:

For example, if I have a method called account_balance, it would be nice to do something like this in my module (i.e. the module that gets included into the Class):

module CustomClient
  def self.included base
    base.class_eval do
      def account_balance
        send_alert_email if balance < min
        super # Then this would just defer the rest of the logic defined in the original class
      end
    end
  end
end

但是使用class_eval似乎会使super方法脱离查找路径.

But using class_eval seems to take the super method out of the lookup path.

有人知道如何解决此问题吗?

Does anyone know how to work around this?

谢谢！

推荐答案

我认为有几种方法可以完成您想做的事情.一种是打开类并为旧的实现加上别名:

I think there are several ways to do what you're wanting to do. One is to open the class and alias the old implementation:

class MyClass
  def method1
    1
  end
end

class MyClass
  alias_method :old_method1, :method1
  def method1
    old_method1 + 1
  end
end

MyClass.new.method1
 => 2 

这是猴子补丁的一种形式，因此最好在适度.另外，有时需要的是一个单独的辅助方法，该方法具有通用功能.

This is a form of monkey patching, so probably best to make use of the idiom in moderation. Also, sometimes what is wanted is a separate helper method that holds the common functionality.

编辑:有关更全面的选项，请参见JörgW Mittag的答案.

EDIT: See Jörg W Mittag's answer for a more comprehensive set of options.

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