CSC321.01 2016S, Class 09: Software as a Service ================================================ _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 ----------------