Create a new instance of parent's class variable for each child class

Question

I have this parent class:

class ListBase
  @@list = []

  def self.list
    @@list
  end
end

I'm trying to create two child classes like so:

class Child1 < ListBase
end

class Child2 < ListBase
end

I was under the impression that each of these child classes will have their own @@list class variable. However, I get this:

Child1.list.push(1)
Child2.list.push(2)
Child1.list # => [1, 2]
Child2.list # => [1, 2]

which means the child classes share the @@list from the parent class.

How can I create a separate class variable for each of the child classes without repeating?

Answer 1

As @CarySwoveland comments, in your use case, you should use a class instance variable:

class ListBase
  @list = []

  def self.list
    @list
  end
end

Not even sure why you thought of using a class variable for your use case.

Answer 2

You are using class variable through class method (getter/reader).
So you can override that method in derived classes and use own class variable for every derived class.
Not fun, but that how class variables works, they are shared within a class and derived classes as well.

class ListBase
  def self.list
    @@base_list ||= []
  end
end

class ListOne
  def self.list
    @@one_list ||= []
  end
end

class ListTwo
  def self.list
    @@two_list ||= []
  end
end

ListOne.list << 1
ListTwo.list << 2

puts ListOne.list
# => [1]
puts ListTwo.list
# => [2]