[ruby-talk:16871] Re: Something strange with Ruby's inheritance mechanism

Just curious, what did you expect to happen?  What model do you hold in your 
head concerning names and inheritance that is violated by misnaming an object?

On Monday 25 June 2001 18:50, you wrote:
> As Ruby beginner, i try some "canonical" OO scripts. Doing so, I've
> noticed some strange behaviour in inheritance mechanism (from my point
> of vue). Considering a base class Employee :
>
> class Employee
>   attr_reader :name, :age, :salary
>   attr_writer :name, :age, :salary
>   def initialize(name, age, salary)
>     @name   = name
>     @age    = age
>     @salary = salary
>   end
>   def to_s
>     "Name: #{@name}, #{@age}, #{@salary}"
>   end
> end
>
> Considering Manager, an Employee's subclass
>
> class Manager < Employee
>   attr_reader :grade
>   attr_writer :grade
>   def initialize(name, age, salary, grade)
>      super(name, age, salary)
>      @grade = grade
>   end
>   def to_s
>    super + ", #{@grade}"
>   end
> end
>
> A Manager "is a" Employee, reverse is not true (that's the classical
> assertion...)
>
> In Ruby, it's legal to assign an Manager to an Employee with
>
> anEmployee = aManager
>
> anEmployee is now a Manager... I know Ruby doesn't care about type
> checking and i'm aware of the fact that both names are references,
> but, when it comes to classes, it hurts my inheritance conception. Is
> there a way to avoid this behaviour or is it a "feature" ?