Finished the Pokemon Scraper Lab Bonus tests

• Named and optional arguments and metaprogramming facilitate saving objects to a persistent data store
• SQLite gem DB queries return an array of rows, of which the rows are arrays of columns

Completed the 2 ORM mapping labs.

• We setup DB[:conn] constant hash in environment.rb and use it to talk to the database.
• The example ORM initializes the object's id to nil so we can write it after the db has generated it with its autoincrement feature. We set the instance varible directly inside a save method, since it's an attr_reader.
• Tables represent Classes and rows instance objects

ORM mapping to table lab
ORM mapping db to Ruby object lab

Completed the Updating Records in an ORM lab.

• Implemented the find or create pattern with the db
• instantiate object, save to db, set db-generated key field in object
• save all attributes to db when updating

Completed Bringing it all Together lab.

• prevent duplication via find or create methods
• reinforced the pattern of mapping an object to a db row, then writing the unique identifier generated by the db
• that unique identifier should be an attr_reader vs accessor, because we don't want it changed once the db writes it
• we set it using instance variable in a .save method

Completed Dynamic ORMs lab

• The pattern of first creating the database table and having your program do all the work of writing your ORM methods based on that table is exactly how we'll develop web apps in Sinatra and Rails
• It seems like a best practices to put the IF (NOT) EXISTS constraints on creating and dropping db tables.
• introduces the #results_as_hash method of the SQLite3 gem that returns database rows as a hash using the column names as keys, instead of an array of array rows
• PRAGMA table_info("#{table_name}") sql keyword to get the column names of a table.
• the table_name class method doesn't require self when in the Class context(ie another class method)
• Array#compact removes nil values
• Using self.class to refer to class methods inside instance methods
• ORM insert methods ignore nil columns, since the id hasn't been generated yet
• ORM update methods ignore the id column. since it's an attr_accessor due to metaprogramming, we account for it here so we don't overwrite the original value.

Completed Dynamic ORMs with Inheritance

• Why is it useful to have a generic ORM class that others can inherit from?
• We don't have to code useful methods like find_by_name or save, we can just inherit from a generic super class.
• Describe the code used to construct such a class
• Uses class methods and the self keyword to extract the sub class names.
• The .find_by_name method in the lab has a typo
• sql = "SELECT * FROM #{self.table_name} WHERE name = '?'"
• The '?' gets treated as a string literal instead of a bind parameter
• several mentions of bind_param in the traceback, which is a clue.

Watched an ORM scraping video, and got the most useful explanation of the #tap method

• self.new.tap {|room| room.id = id} #tap returns the object to the left of it, but it gives you access to it as a block scoped variable. It eliminates the need for a dangling return. Finished ORM section, started on ActiveRecord
• the #send method allows us to access instance variables programmatically.