Does 'attr_reader' make a local variable available throughout a class?

Question

Why is the type variable available in the is_a_peacock? method in the following?

class Animal
    attr_reader :type

    def initialize(type)
        @type = type
    end

    def is_a_peacock?
        if type == "peacock"
            return true
        else
            return false
        end
    end
end

an = Animal.new('peacock')
puts an.is_a_peacock? # => true

Why does commenting out the initialization of @type make type unavailable?

class Animal
    attr_reader :type

    def initialize(type)
        #@type = type
    end

    def is_a_peacock?
        if type == "peacock"
            return true
        else
            return false
        end
    end
end

an = Animal.new('peacock')
puts an.is_a_peacock? # => false

Answer 1

"Why does commenting out the initialization of @type make type unavailable?"

It does not. Method type is available. Just not initialized. Because you commented that out.

If method type wasn't available, your program would crash. (As it does when you comment out the attr_reader).