Ruby Classes Lab

Remember:

1. Ruby objects are created by Ruby classes
2. A Ruby class is a template for creating a Ruby object
3. A Ruby object contains methods from its class and maintains its own state

Make an object from a class by using

some_new_object = SomeClass.new (optional arguments)

1. Classes

Watch the optional short video here. 6 mins 23 seconds.

Create Muppets

1. Create a Muppet class that takes in a name and run puts "This muppet is called #{name}!" inside initialize.
2. Assign the muppet a random color on initialize. Hint: make a small array and use .sample

Create Birds

2. Create a Bird class that takes in an adjective and a name and puts "#{name} is a(n) #{adjective} bird!" inside initialize.
3. Assign the bird a species at random on initialize. Hint: make a small array and use .sample
4. Here is an array of bird species, for your convenience

  ['Belted Kingfisher', 'Yellow-Billed Cuckoo', 'White-Cheeked Pintail', 'Cinnamon Teal', 'Lesser Scaup', 'Bufflehead', 'Common Goldeneye', 'Fulvous Whistling Duck', 'Hooded Merganser', 'White-Winged Scoter', 'Chimney Swift', 'Rufous Hummingbird', 'Chuck-Wills-Widow', 'Whip-Poor-Will', 'Albatross', 'Ruddy Turnstone', 'Piping Plover', 'Killdeer', 'Laughing Gull', 'Marbled Godwit', 'Least Tern', 'New World Warbler']

2. Methods

Watch the optional short video here here. 8 mins 22 seconds.

Muppet methods

• Add methods to your Muppet

  • Add a honk method to your muppet that puts "#{name} is making a honking sound!". Test that it works, comment out your test code.
  • Test the following to make sure it gives the expected output:

q = Muppet.new("K-Rad")
q.honk

• Add a flail method that puts "#{name} is flailing its arms!". Test that it works.

Bird methods

• Add methods to your Bird

  • Add a hungry method that puts "#{name} wants some regurgitated worms!". Test that it works.
  • Add a fly method that puts "Flap! #{name} is taking flight!". Test that it works.
• Make your bird's adjective and name accessible (both reading and writing). Test that this works.

3. Inheritance

Watch the short video here. 6 mins 56 seconds.

Exercises:

1. Create a class called Dessert that has instance variables of @name and @sugar_content
2. Give it an instance method of eat that puts "Yum! This #{name} is sooooo delicious!"
3. Make two new classes called Pie and DeepFriedDessert that inherit from Dessert
4. Give the DeepFriedDessert its own eat method that instead puts "Yum! This #{name} is sooo...ack! ugh! *heart-attack*"
5. Make a new class IceCream that inherits from Dessert. Use super to get the instance variables of @name and @sugar-content. Also give IceCream its own unique instance variable of @toppings

4. The Universe

Reps with Classes

Universe Part One

What's in a Class? A class can contain any number of variables and any number of methods. That is, any number of things and any number of actions. Therefore, let's make a Universe simulator! ;)

1. Make a Class called Universe.
2. Universe takes three parameters, item1, item2, item3: these are the three things within this universe we are making-- they could be anything: suns, galaxies, dust, people, lossless mp3s, justice, temporal lobes, etc. Save these things into an array called @items.
3. Give the initialize method an instance variable @expanding = true
4. Give the initialize method an instance variable @conservation = true
5. Give the initialize method an instance variable @crunched = false
6. Make a method see_all_things that will print out all the items in this universe. Test it out.
7. Make a method called create that takes a parameter new_item and will add the new item to the universe (in the @items array). If @conservation = true then one random item in the universe is replaced by the new thing. If not, then a new thing is added to the @items array.

Universe Part Two

8. While @conservation is true, run the create method to add a "mosquito" to your universe. Keep running it until all of the items in your universe are mosquitoes (they should be randomly replaced). You now have a mosquito universe. :(
9. Time to make a parallel universe. Make a new instance of your universe called parallel, and put three new things into it.
10. Make a method check_density that changes expanding to false if there are more than ten things in the universe (more than ten items in the @items array). This will mean that the universe is now contracting under its own gravity. We'll come back to this in a minute . . .
11. Make a method called energy_conservation that changes conservation from true to false if all items in the @items array are identical. Hint: check out the .uniq method.

Universe Part Three

12. Make a method called crunch? wherein, if expanding equals false, goes through each item in the @items array, sets it to nil and prints a string saying the name of the item and that it has been crunched due to gravity. When the entire contents of the array are nil, set the array itself to nil and print "The Universe has ended." If the universe has ended, set @crunched to true.

13. Write your Universal Simulator that runs the following steps in a loop until the Universe has ended. The Universe has ended when @crunched is true. You might want to make @crunched available with attr_accessor. Start by making a new instance of the Universe.

    • print the contents of @items
    • add an item to @items
    • check conservation
    • check density
    • crunch?

Possible output:

spam
github
lava
spam has been crunched due to gravity
github has been crunched due to gravity
lava has been crunched due to gravity
radio waves has been crunched due to gravity
The Universe has ended
=> true

HUNGRY FOR MORE?

5. Class Methods and 'Self'

Watch the short video here. 8 mins 28 seconds.

Exercises:

• Experiment with self

  • Add a class method self.what_is_self to your Muppet class and have it p self.
  • Add an instance method what_is_self to your Muppet class and have it p self.
  • Try calling both of these methods in Pry and see what they return.

• Add a class method to make baby Muppets

  • In your Muppet class, add an instance variable that gives your Muppet a characteristic or quality such as 'zany', 'quiet', 'twitchy' to the instance of the Muppet.
  • Add a class method of self.make_muppet to your Muppet class that takes in two Muppets and returns a new Muppet.
  • The new Muppet should have the color of the first Muppet and the quality of the second Muppet. Make some Muppets.