CSC 321.01, Class 06: An introduction to Rails

Overview

• Preliminaries
  • Notes and news
  • Upcoming work
  • Good things to do
  • Questions
• Version control systems
• Making better use of GitHub
• Model-View-Controller
• Other rails issues

Preliminaries

Admin

• Mentor session Sunday and Tuesday night
• How long did Hartl 1 take?
  • Observation: When things go right, it’s reasonable. But when things go wrong, it’s really hard to figure out why.
• The Friday PSA will happen in CSC 322
• Don’t forget to add yourself to the homework channel!

Upcoming work

• Hartl 2 due Sunday at 10:30pm.
  • This should take about the same amount of time as the first Hartl assignment.
• Hartl 3 due Tuesday at 10:30pm.
  • The response part of this assignment will not be available until Sunday (approximately)

Good things to do (Academic/Artistic)

• Rebecca Wingo: How to Harvest History. Friday Feb. 2, 4pm, Burling Library Lounge.
  • Workshop: Saturday Feb. 3, 10-1, DLab
  • Register for workshop at https://grinnell.formstack.com/forms/wingo_workshop
• Movie Sunday: I Am Not Your Negro, 4pm in the Strand
• CS table Tuesday: TBD
• CS extras Thursday: The evolution of CSC 151

Good things to do (Other)

• Indoor Track and Field Saturday at 9:30 am.
• Swimming Saturday at 1:00 pm.
• Tennis meet Sunday at 10:00 am.
• Posse Plus Retreat Reflections, Community Hour next week (Tuesday, 11am, JRC 101)

Questions

Version control systems

• Allow you to keep track of old versions of whatever you are writing (usually code).
  • Safe to make changes.
  • Encouragement to describe changes.
  • Ability to see changes.
• Support collaboration.
• Allows others to learn about you. (The joy of mediocre data science.)
• Good programmers use a version control system to manage the complexity of collaboration (and more).
• As you develop as a software designer, you should also develop more sophisticated ways to work with your version control system.

Making better use of Git

Simplistic view

• git pull
• Make changes
• git add .
• git commit . -m "asdf"
• Make sure the changes work
• git pull
• Make sure the changes still work
• git push

Improvements to the workflow

• Make sure the changes work!
  • Use a tool that checks for you
• Do your work in a branch so that you can have a longer series of steps while still being able to commit.
  • Empowers you to work on partial code.
  • Branches are also nice for small tests.
• Add/commit individually (by name) rather than everything.
  • Don’t pollute the repo.
  • Don’t risk information.
  • Check what files have been added or changed with git status
  • Sam prefers that you never use anything like git add . or git add -A or git commit -a.
• Send pull requests rather than pushing the data.
• These days, Sam does a lot of git stash save and git stash pop.
• I sometimes find that I need to use git diff to recall what changes I made.
• The .gitignore file tells Git not to track things.
• git log is useful to get a quick list of what you did (provided you choose good log messages)

Model-View-Controller

What is it?

• Segementation of three parts of a typical application.

Why do we use it?

• Components can be swapped out
  • Can change the UI
  • Can change the model
  • Rarely change the controller
• Might provide some more security; limit the flow of data.
• With well-specified APIs, you can work on the three parts separately. (Often why we segment.)
• Should be easier to modify code.
• Makes it easier to read / understand.

How does MVC relate to the three-tier architecture?

• Both break the world up into three parts (and a similar three parts).
• But three-tier provides more limited communication between the parts.

Other Rails issues

• An MVC model for building Web applications.
• Requires/benefits from a series of magic incantations.
• “Convention over configuration”
  • Which files are created
  • Where it looks for data, etc.
  • Naming conventions, including an important “s”
• When things go well, it’s easy.
• When you know it well, it’s easy.
• When you are a novice and things go wrong, it’s a PITA.
• Benefits from a rich plugin system.
• Normal development cycle: Develop on one machine, deploy on another.