From: Joel VanderWerf <joelvanderwerf@...>
Date: 2010-11-03T03:04:37+09:00
Subject: Re: the dark side of inherited methods

On 11/02/2010 10:02 AM, Josh Cheek wrote:
> On Tue, Nov 2, 2010 at 11:19 AM, James Edward Gray II<james@graysoftinc.com
>> wrote:
>
>> Of course, inheritance has it's place and uses but I feel it's definitely
>> overused.
>>
>>
> Can you give some examples of where it has its place? I have been trying to
> think of one, and can't. I realized the only time I ever subclass anything
> is ActiveRecord::Base (and I'm not really sure what that offers over
> modules, DataMapper uses modules, for example).

The shortest example that occurs to me:

class A < Struct.new :x, :y, :z
   def length
     Math.sqrt(x**2 + y**2 + z**2)
   end
end

That only saves a couple of keystrokes compared to:

A = Struct.new :x, :y, :z
class A
...

but it's cleaner IMO. Also, it allows you to do this:

   def x=(new_x)
     raise ArgumentError if new_x > 100
     super
   end

In the "A=Struct.new" approach, you have to muck around with alias to 
get the same effect.