ad1-day7.md

Very Best Debug

• README
• debug home page
  • Reading - Better Errors
    • banner
    • highlighted line
    • console
  • debug it
  • rails sample_data
• rails grade
  • read test title
  • click on test
  • examine test
• Handy to keep up RCAV flowchart image
• Spend at least 30 minutes on this and pg-gui if you haven’t finished
• then we’ll look at something pretty cool and exciting
  • (2-2:15)

Refactoring MSM 2

• bin/server visit actor details
• rails sample_data
• go over actor details -> filmography view
• we defined methods that looked up associated records
  • open actor#characters
  • open character#movie
  • open movie#director
• benefits
  • if we define them first, speeds up view template
  • other teammates can just use them
  • avoid typos re-writing queries everywhere
• We can use these methods anywhere that we have a record
• any questions?
• Each of these associations represent one side of a 1 to N
  • director#filmography vs movie#director
• Look at movie#director vs character#movie
  • very similar
  • The only things that differ are the
    • name of the method
    • the name of the foreign key column
    • the name of the class
  • Define Character#actor by copying movie # director
• Similar relationship btw character and actor
  • Define Character#actor by copying movie # director

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• We can define these types of methods
  • in a better, more powerful, and concise way
• If only three things change between these methods
  • Rails will make our lives easier by
  • letting us use a method that will define other methods for us
• belongs_to(:movie, {…})
  • comment out both
  • visit page
  • uncomment new one
• Can you see how Rails can infer and deduce how to define this the director method using the information we gave to belongs_to?
• A non-technical teammate can read and understand the relationship between the two tables
  • Movie belongs to one director
  • Character belongs to one movie
• What’s the benefit?
  • even less chance for typos
  • power
    • joins
      • I can query Characters using columns in the character table
      • what about using columns in the movies table?
      • Character.joins(:movie).where("movies.title LIKE '%The Dark Knight%')
• What do you think?
• Exclude keys in belongs_to
  • what do you think will happen if I remove the class name?
    • put on debugging hat
  • convention over configuration philosophy
• This is one type of association method, where our starting record contains a foreign key that connects to another table
  • the other side is different
  • Director#filmography
  • Define Movie#characters by copying Director # filmography
• has_many(:characters) method constructor

We have these relationships

Director -> Movies
Actor -> Characters
Movie -> Characters

# Define:
characters method in Actor
actor method in Characters

characters method in Movie
movie method in Character

director method in Movie
filmography method in Director

• Break
• any questions?
• go over solutions

association accessors demo

• find link in readme
• watch me and ask questions
• add models (after we come up with our data model)
• start wizard
  • to help us determine how to define these association methods
  • direct vs indirect
• tool to walk you through how to define association the long way
  • using the shortcuts
  • and if we can make them more concise
• interactive chapter for any of your projects

Many to Many

• go over actor#filmography
• went over something similar before with movie cast, not used in this app
• different type of association— -> slides
• there isn’t a foreign key column used there’s no class name
• many to many, these two tables are indirectly related through two existing associations
• we can use has_many for this as well