Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
• Learning from Video.
• DRY.
• Data Modeling.
• Thinking about SaaS.
• Rails, revisited.

Preliminaries

Admin

• 13 hours with alums was a bit overwhelming yesterday and I'm a bit behind.
• Friday PSA.

Upcoming Work

• SaaSBook 7 for Monday.
  • Yes, I will ask you about your experience watching videos.
• Reading Journal for Monday (due Sunday at 8pm)
  • Subject: Reading Journal for Class 10 (Your Name)
  • What is the most important thing you learned about cucumber as a tool for behavior-driven development?
  • What is the biggest difference betwen the agile approach to requirements and the plan-and-document approach to requirements?
  • Which of the BDD pitfalls do you think you or your team will have to be most careful about? Why?
  • Do you have any questions you need to resolve before you use cucumber and BDD? If so, what are they?
  • Citation: Questions are based on journal excellent questions from JLND, made less so by SamR.
• Description of BadSpuds for Monday (due Sunday at 8pm)
  • Subject: "Design of Bad Spuds (Your Name or Names)"
  • Suppose you are building a movie review database. What tables will you need, what fields do you have in each table, and what are the relationships between the tables?

Good Things to Do

Academic

• Thursday convo: Hilary Mason '00
• Thursday extra: Hilary Mason '00

Peer

• Track Saturday! NBB runs at 11am.

Miscellaneous

• Vote in new VPSA elections.
• High School Large Group Speech Presentations Saturday at 6:30 p.m. at the high-school auditorium. Sam will reimburse you for the $5 entry fee (or give it to you in advance).

Questions

Learning from Video

Advantages of Video as compared to Book

• The book is very dense.
• The videos are more engaging (or at least less boring).
• Faster, particularly if you learn how to use the speed controls.
• It's even more passive than reading!

Disadvantages of Video as compared to Book

• When you are watching at 4x speed it's really hard to take notes, whereas books stop naturally when you turn away from them to take notes.
• Crappy captions are completing confusing and detrimentally distracting. (Don't worry. The justice department is on it. Armando will probably be in jail soon.)

Similarities

• Notes? What notes?

DRY

• Don't Repeat Yourself. (Damn, if I hadn't fast-forwarded through that point I would have remembered it.
  • Don't Repeat Yourself. (Damn, if I hadn't fast-forwarded through that point I would have remembered it.))
• What does it mean to you with regards to coding?
  • Literally!
    • square(2) ... square(2)
  • Don't do the same sequence of method calls.
    • System.out.print (nbb.name + "'s favorite candy is ");
    • System.out.println (faves.lookup(nbb,"candy"));
    • System.out.print (pw.name + "'s favorite candy is ");
    • System.out.println (faves.lookup(pw,"candy"));
  • Alternate
    • void candy(Person p) { System.out.print (p.name) ... }
  • Often good to generalize your code.
  • Also fix with things like inheritance.
  • Also fix with sensible loops.
    • Instead of candy(nbb); candy(pw); candy(atm); ...
    • Use [nbb,pw,atm].each(candy)
• What aspects of Rails and Ruby help with DRYness?
  • The ability to include template code in Web pages.
  • Mixins in Ruby
  • The better version of CSS
  • Metaprogramming
  • Higher-order programming with things like yield
  • Partials - generalized code
  • Inheritance
  • Everything is an object (as relates to inheritance)
    • Maybe Duck typing
  • Scaffolding
  • Gems
  • Normal programming language features: Loops, subroutines (functions)
• How do you DRY out your code?
  • Use the above.
  • If you program by copy-paste-change, DRY out your code.
  • In practice, the first time you copy-paste-change is probably okay, if you're just getting something working quickly; but make a note to fix it.

Data Modeling

Typically using a relational model. The term relation is used int two ways:

• A "relation" is what we might think of as a table. If we are describing courses at Grinnell, we might have a Student relation.
  • surname, forename, stuid, classid, semester, grade
• There are relationships between relations
  • Every student has at least three classes. Every class has at least one student. Each student has exactly one student id.
• What kinds of relationships are there between relations?
  • one-to-one: Each student has exactly one student ID
  • one-to-many: each professor has multiple classes, but each class has only one prof.
  • many-to-many: student-class relationships
• Problem: How do we represent these relationships (in a database)?
  • Fortunately, if you describe them correctly in your Ruby data model, you don't have to worry about it.
  • Unfortunately, Sam thinks you should need to worry about it anyway.
• One-to-one: Usually put in the same table.
• One-to-many: Associate an identifier with each thing, and use that identifier in the other table
  • Faculty table: facid, faclastname, facfirstname, facage,
    facsalary, ...
  • Course table: courseid, coursename, ..., facid
• Many-to-many
  • Option one: Use the same idea as above.
    • Student table: stuid, stulname, firststuname, ..., courseid
      • 33123, "Smith", "Jordan", 123
      • 33123, "Smith", "Jordan", 431
    • Course table: courseid, coursename, ..., facid
      • 123, "Underwater Basket Weaving"
      • 421, "Lifesaving"
  • Better option: Add another table of stuid x courseid
    • Student: 33123, "Smith", "Jordan"
    • Course: 123, "Underwater Basket Weaving"
    • Enrollment: 33123,123
• Our database manager helps us with all of this.

BadSpuds - Movie Rating System

• What tables?
• What relations between those tables?

Thinking about SaaS

Rails, revisited