To Lecture Notes

IT 232 -- 10/14/15

Review Exercises

1. What does the spaceship operator have to do with sorting objects?
   Ans: If <=> is defined for a model, then an array of objects from that model can be sorted with the Array sort method.
2. How does has_and_belongs_to_many work?
   Ans: It defines a many-to-many relationship. For example, if a many-to-many relationship is defined for Student and Course using the table courses_students, then if s is a student object, s.courses returns an array of all of the courses in which the student s is enrolled. Similarly, if c is a course object, c.students returns an array of the students enrolled in the course c.

Project 3

• Suggestions for Project 3 models:
  
  1. Owner, Photo, Like. Owner is the same as follower
  2. Owner, Follower, Photo, Like. Set up a one-to-one relationship between Owner and Follower.
  3. Owner, Follower, Photo. Use a followers_photos table (many-to-many-relationship).
  4. Follower, Photo, Like. Recommended. Similar to the School1 Example.

More Examples

1. Look at the LikesSite and LinkIcons Examples.

Using ActiveRecord

• ActiveRecord Queries
• Practice Problem: Set up a scaffold-based project with model Photo, fields description, and file_name. Write a loop that displays all of the photos in a view in order of most recent to least recent. Use these photos for your project: dogs-owners.zip.
  Ans: See the PhotoGallery Example.