How to Access a Ruby Class Variable From Outside the Class?

In Ruby, you cannot directly access class variables (i.e. @@variable) from outside the class:

class Foo
    @@bar = "foobar"
end

# undefined method `bar' for Foo:Class (NoMethodError)
puts Foo.bar

To access a class variable, you must create a class method that returns the value of the class variable:

class Foo
    @@bar = "foobar"

    def self.bar
        @@bar
    end
end

puts Foo.bar #=> "foobar"

It is also possible to access a class variable from a class instance by creating a getter instance method.