CF 3.5 | oop, pt. 2 (instance methods, inheritance, etc._

3.5.rb

str.is_a?(Object)
str.class

# here we extend Ruby's string class meaning that all strings in the environment will belong to this class
class String
	def star
		self + " *"
	end
end

puts str.star
puts "yay".star

class String
	def self.announce
		puts "I am the String class"
	end
end

# The class above uses the keyword self, which refers to the instance of the class on which the method is called (the particular object). Class methods are methods that work on the class rather than an instance of the class.
puts String.announce # works
puts "hello".announce # error

cat.rb

# everything that Cats and Dogs have in common go in this Pet class
class Pet
	attr_reader :color, :breed, :name
	# There is no need for a separate attr_writer and separate attr_reader for name because attr_accessor can combine those methods into one (DRY)
	# attr_writer :name
	attr_accessor :name

	def initialize(color, breed)
		@color = color # Instances variables are available to other methods inside of this class. This is unlike local variables, which only exist inside the method they're called in.
		@breed = breed
		@hungry = true
	end

	def feed(food)
		puts "Mmmm, " + food + "!"
		@hungry = false
	end

	def hungry?
		if @hungry
			puts "I\'m hungry!"
		else
			puts "I\'m full!"
		end
		@hungry
	end
end # end Pet class

# Cat class which inherits from Pet class
class Cat < Pet
	def speak
		puts "Meow!"
	end
end

# Dog class which inherits from Pet class
class Dog < Pet
	def speak
		puts "Woof!"
	end
end

kitty = Cat.new("grey", "Persian")

puts "Let's inspect our new cat:"
puts kitty.inspect
puts "What class does our new cat belong to?"
puts kitty.class
puts "Is our new cat an object?"
puts kitty.is_a?(Object)
puts "What color is our cat?"
puts kitty.color # if the class has not attr_reader, this returns and error because 'color' is an undefined method for class Cat. When an attr_reader is added to the class, the error goes away.
# kitty.color = "orange" # this will return an error if the Cat class doesn't have an attr_writer
puts "Let's give our new cat a name"
kitty.name = "Betsy"
puts kitty.name

puts "Is our cat hungry now?"
kitty.hungry?
puts "Let's fed our cat"
kitty.feed("tuna")
puts "Is our cat hungry now?"
kitty.hungry?

puts "Our cat can make noise"
kitty.speak

# instance of Dog class
puppy = Dog.new("white", "Husky")
puppy.speak # "Woof!"
puts puppy.color # "white"