Rails活动模型继承

Question

I think what I'm trying to accomplish is multi table inheritance but I'm not sure how to properly implement it.

I want to start with a base class Device that will contain all the common fields such as name and enabled.

class Device
  # in app/models
  # Fields
  #   String name
  #   boolean enabled
end

I then want to create abstract classes for the different device types such as Light that inherits from Device

class Light < ActiveRecord:Base
  # in app/models
  # Fields
  #  String type

  include Device

  def on
    raise NotImplementedError
  end

  def off
    raise NotImplementedError
  end
end

I then will have classes for specific devices such as X10Light and ZWaveLight that will define the specifics for each device and implement the abstract methods.

class X10Light < Light
  # in app/models
  # Fields
  #   String serial_number

  def on
    # fully implemented on method
  end

  def off
    # fully implemented off method
  end
end

My goal would then be to use it like the following

light1 = X10Light.new
light1.serial_number = "x1"
light1.save

light2 = ZWaveLight.new
light2.serial_number = "z1"
light2.save

all_lights = Light.all
all_lights.each do |light|
  light.off
end

I think the way I have things planned out this is possible, but I think have some of the implementation incorrect. I'd appreciate any help ironing out the details on this. Thanks!

Answer 1

You can use Single Table Inheritance, you will need to create a model Device which will hold all your fields plus a reserved column named type , where rails will store the class name of the concrete instance.

rails g model Device type:string ... other fields (ie columns for device, light, x10light) ...

class Device < ActiveRecord:Base
  ...
end

class Light < Device
  ...
end

class X10Light < Light
  ...
end

The downside of using STI is that you end up with a table which has all the columns of the tree of your inheritance.