Week 2 - Overview
Students should be comfortable with the following at the end of this week:
- Agile Development
- Testing and TDD
- Blocks and Enumerable
- Inheritance, Composition, and Modules
Important Links
Tuesday - Inheritance and Testing
Problem of the Day: Vehicle Inheritance
- Random Items
attr_reader, attr_accessor- Splat operator (
*)
- predicate methods
?
- Inheritance
- Exploration: Start with Float object. Explore superclasses and classes.
- Begin in-class work on Vehicle exercise.
- Exceptions
- Review how the exception problem was solved over the weekend.
- Explore inheritance tree for exceptions
- Example code: divide by zero in a method
- Raising exceptions yourself
- Inventing exception classes
- Gems
gem listgem install- byebug
- Testing
- Show tests for the Vehicle class. Use code already built.
- Build out “12 Days of Christmas” for its test suite.
- Sliming
- Git
- Reason: Sharing code with others
git clone.gitignore files- Forking
- GitHub collaborators
git pull
Lecture Notes/Links
Evening Reading
Assignment - IN PAIRS
Begin Battleship. Get tests 01-18 to pass.
Wednesday - Modules and Composition
- Human Learning: Feedback Cycles and Agile Development
- ON BOARD: Iteration
- DIAGRAM: Finding a path to a moving point
- Random topics
- You can return objects when true/false is expected (e.g.
ship.fire_at(x, y))
- Ternary operator (e.g.
object.is_true? ? "Yes" : "No" )
- Class variables - DON’T
- OO:
public vs private
- Example: Daisy is a Builder. She has many steps she takes to build a house.
- We don’t want to micromanage her and tell her HOW to build the house; we just want to tell her to build it and let her figure out the details.
- Tell, don’t ask
- Inheritance - is-a
Problem of the Day 1: Vehicle Modules
- Modules - acts-like-a/has-a-role
- Also, use of modules for namespacing
- Example: IronYard module with Instructor and Student classes. Iron Yard students don’t sleep, but a Student outside the module does.
- Example: Bass.
- Make two classes with the same name. One for the fish and one for the instrument.
- Each should have a
maximum_length method, but they should return different things
- You should also be able to call
Fish::PHYLUM and get back "Chordata"
Problem of the Day 2: Vehicle Composition
- Composition - has-a
- Sometimes you don’t want the class itself yo know how to do everything that is asked of it. Instead, you want the class to be able to ask its components to answer questions for it.
Lecture Notes/Links
Evening Reading
Assignment - IN PAIRS
Continue Battleship. Get tests 19-31 to pass.
Thursday - Regex, Enumerable, and Blocks
Problem of the Day: Find Names
- Random topics
- Show how easy refactoring is with good tests. Move arrays out to methods.
- Don’t overdo it on instance variables
- Keyword arguments
- Monkey Patching: Change a string to add
.to_pig_latin
- Calling private methods with
.send()
- Arrays as stacks and queues (
.push(thing), .pop, .unshift(thing), .shift)
- Regex
- XKCD on Regular Expressions
- Example: Did the user just type in a number?
\d*, +\A, \z OR ^, $- Example: Does a string store an IP address?
()[]|{1, 3}- Literals
- Example: Does a string contain a person’s name?
\w\s\W, \D, \S- Example: Does a string contain a phone number?
?- In your spare time: how about email addresses?
- Using regex in Ruby
.match.scan, .sub, .gsub
- Enumerable
.each.each_with_index.map.select / .reject.all? / .any?.reduce
- Inline blocks (e.g.
array.map {|a| a.class} instead of do ... end)
Lecture Notes/Links
Evening Reading
- Preview Reading: Blocks and Procs - Only required down through “Procedures, AKA, Procs.” Read “Lambdas” and beyond if you dare.
Assignment - IN PAIRS
Complete Battleship. Get all tests to pass.
Friday - Test-Driven Development
Problem of the Day: OddArray
- Agile Development
- DIAGRAM: Feedback cycles of escalating size.
- ON BOARD: Feedback loops:
- Project post-mordems
- Iteration retrospectives
- Frequent client meetings
- Daily standups
- Run code and tests often, ideally after every change.
- Pair programming
- ON BOARD: Debugging is everywhere
- First: squint hard
- Second: read the error messages
- Third: Test your assumptions
- Fourth: Break the problem into smaller problems and solve them individually
- Fifth: Google
- Two types of resources: tutorials and answers.
- Stackoverflow is great for answers.
- Blogs (and Rails Guides) are great for tutorials.
- Be as specific as you can about which technologies you’re using.
ActiveRecord::Base is a better start to your search than Rails
- You can try questions (e.g.
How do I use ActiveRecord?)
- Limit to last year
- Use Google to dig deeper into someone else’s docs (e.g.
weather underground api sunrise)
- XKCD on Old Forums
- Blocks/Procs/Lambdas/Methods
- Methods as objects
m = method(:my_method)m.call
- Blocks
- Code snippets that we pass to things like
.each or .map
- Passed in to a method using
{} or do ... end
yield to a block inside a method
- Procs
- Crystalized blocks
p = Proc.new {...block_stuff...}- Passed in to a method using
method(&p)
- Called from within the method with
parameter.call
- Lambdas
- Procs with their own scope on the call stack
return is limited to returning from just the lambda, not the method calling the lambda.
- TDD
- Four steps:
- Write a test which tests one (isolated) new behavior
- Make sure your new test fails
- Write code to make your test pass
- Refactor while keeping all tests passing
- Run through example TDD with ye olde Albums and Artists.
assert_in_delta- Expect tests to run randomly (third class method here)
- (Second contender for the best method ever)
- Human Learning
- ON BOARD: Estimating is hard.
Lecture Notes/Links
Evening Reading
Weekend Assignment
Employee Reviews
