Rails course day 3
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The document outlines the third day of a Ruby on Rails course, focusing on ActiveRecord, which encapsulates database access and domain logic. Key topics include model associations, validations, and various database operations such as creating models and handling relationships. An overview of the query interface and its functionalities, including methods for finding and ordering records, is also provided.
![Rails g model
<model_name>
[field:type, ]
Creates model file
Creates model test
Created migration
file.](https://image.slidesharecdn.com/rails03-150918081227-lva1-app6891/85/Rails-course-day-3-8-320.jpg)
Rails course day 3
- 2. M for Model
- 4. Active record and MVC What’s ActiveRecord ? What to expect from ActiveRecord Model. associations. inheritance. validations. OO DB operations. Convention over configuration.
- 5. Active Record An object that wraps a row in a database table, encapsulates the database access and adds domain logic on that data.
- 6. What to expect from ActiveRecord Model? associations. Relations to different models to simulate one2many, many2one self joins, etc.. inheritance. also is considered as relation however it’s parent-child relationship between models. validations. validation logic OO DB operations. Business logic example: ahmed = User.last ahmed.joined_course(“math”)
- 7. Convention over configuration Model class name and table name Foreign and primary key convention: FK: <table_name>_id PM: id
- 8. Rails g model <model_name> [field:type, ] Creates model file Creates model test Created migration file.
- 9. Associations belongs_to has_one how is that different than belongs_to ? through has_many through has_and_belongs_to_many
- 11. has_one has_one is One2One connection. single model has_one <model> No FK required in model, it’s pointed in the other model. through is the intermediate junk table.
- 13. has_many through :model VS. has_and_belongs_to_many
- 14. Self Join class_name foreign_key class Employee < ActiveRecord::Base has_many :subordinates, class_name: "Employee",foreign_key: "manager_id"
- 15. Validations Built-in validates :name, presence: true, length: {minimum: 3} Class Validator, EachValidator Template design pattern Methods on:
- 16. Call Backs Before, after and around ->Save Save<- ->Save<- When Create, update, destroy Save, validate Executionorder Destroy Update Create
- 17. Query interface find(id or array(id)) take, first, last find_by(key: value)* where ? for sql injection hash conditions Ordering Selecting Group and Having includes* limit and offset *find_each will be used with huge amount of records *includes will eager load all associated models for less queries.
- 18. Thank you!