What are class variables in Ruby?

What are class variables in Ruby?

Class variables in Ruby are variables that are shared among the class and all its instances. They are defined with two '@' symbols, like this: @@variable_name.

Can you give me an example of how to use class variables?

Sure! Here's a simple example:

class Dog
  @@number_of_dogs = 0

  def initialize(name)
    @name = name
    @@number_of_dogs += 1
  end

  def self.total_dogs
    @@number_of_dogs
  end
end

fido = Dog.new('Fido')
puts Dog.total_dogs  # Output: 1

What’s the difference between class variables and instance variables?

Class variables (@@) are shared across all instances of a class, while instance variables (@) are unique to each instance.

When should I use class variables?

Use class variables when you need to maintain a state that is shared across all instances of a class, like a counter.