如何通过抽象活动记录向子类添加范围 [英] how can I add a scope to subclass class through abstract active record

问题描述

我想要一些子类，它们都应该有一个范围(同名).虽然我知道直接继承是不可能的，但基本思想如下:

I would like to have a few subclasses that should all have a scope (of the same name). Although I know this is not possible with straight inheritance the basic idea is the following:

class MySuperClass << ActiveRecord::Base
abstract_class = true
scope :scopeForAllSubclasses , lambda {|my_var| where(:var => my_var )}
end

class Subclass1 << MySuperClass
#has attribute var
end

class Subclass2 << MySuperClass
# has attribute var
end

所以现在我想打电话

Subclass1.scopeForAllSubclasses123).all

和

Subclass2.scopeForAllSubclasses(123).all

重点是我想要一组类，它们都通过设计实现了这个范围，而不仅仅是因为开发人员决定这样做.

The whole point it that I want a group of classes that all have implemented this scope by design rather than just because the developer decided to do so.

有什么想法吗?

推荐答案

你可以使用 mixin 而不是超类来做到这一点:

You could do this with a mixin instead of a superclass:

module ScopeBuddy
  def self.included base
    base.instance_eval "scope :scopeForAllSubclasses , lambda {|my_var| where(:var => my_var )}"
  end
end

class ClassA
  include ScopeBuddy
end

class ClassB
  include ScopeBuddy
end

这会将作用域注入到每个实例中.

This will inject the scope into each instance.

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