The document summarizes Active Record validations and callbacks in Ruby on Rails. It covers the object lifecycle, an overview of validations and callbacks, validation helpers like presence and uniqueness, common validation options, conditional validation, custom validations, working with validation errors, and displaying errors in views. It also discusses callback classes, observers, and transaction callbacks.

1. The 5th Round of ROR Lab.
Active Record
Validations and Callbacks
January 14th, 2012
Hyoseong Choi
ROR Lab.

2. Contents
• The Object Life Cycle • Callbacks Overview
• Validations Overview • Available Callbacks
• Validation Helpers • Running Callbacks
• Common Validation Options • Skipping Callbacks
• Conditional Validation • Halting Execution
• Custom Validations • Relational Callbacks
• Working with Validation • Conditional Callbacks
Errors • Callback Classes
• Displaying Validation Errors • Observers
in the View
• Transaction Callbacks
ROR Lab.

3. Contents 6th round
• The Object Life Cycle • Callbacks Overview
• Validations Overview • Available Callbacks
• Validation Helpers • Running Callbacks
• Common Validation Options • Skipping Callbacks
• Conditional Validation • Halting Execution
• Custom Validations • Relational Callbacks
• Working with Validation • Conditional Callbacks
Errors • Callback Classes
• Displaying Validation Errors • Observers
in the View
• Transaction Callbacks
ROR Lab.

4. Validation Time Point
Web Server
Controller
Client CRUD Validation DB
ROR Lab.

5. Validation Event
Triggering validations Skipping validations
create • decrement!
• create! • decrement_counter
• save • increment!
• save! • increment_counter
• update • toggle!
• update_attributes • touch
• update_attributes! • update_all
• update_attribute
• update_column
• update_counters
ROR Lab.

6. “new” method
• no validation called.
ROR Lab.

7. Call Validations
• valid? or invalid?
ROR Lab.

8. valid? vs Errors
By definition,
an object is valid if this collection is empty
after running validations.
ROR Lab.

9. Validation Helpers
• acceptance • uniqueness
• validates_associated • validates_with
• confirmation • validates_each
• exclusion
• format
• inclusion
• length
• numericality
• presence
ROR Lab.

10. Common Options
:allow_nil
:allow_blank
:message
:on
ROR Lab.

11. Conditional Validation
:if and :unless
• A Symbol : a method name
• A String : a really short condition
• A Proc : an inline condition
ROR Lab.

12. Custom Validations
• Inherited from Two modules
★ ActiveModel::Validator
★ ActiveModel::EachValidator
★ Get the “record” argument as a
parameter
★ Custom methods & helpers
ROR Lab.

13. Working with Validation
Errors
• errors.messages
• errors[:attr] : for a specific attribute
• errors.messages
• errors.full_messages( or errors.to_a)
• errors.add(:attr, message)(or errors[:attr]=)
• errors[:base] : object’s state as a whole
• errors.clear : intentionally to clear
• errors.size : count of errrors
ROR Lab.

14. Displaying Validation
Errors in the View
★ gem ‘dynamic_form’ ★ Error Messages CSS
.field_with_errors
#errorExplanation
#errorExplanation h2
#errorExplanation p
#errorExplanation ul li
ROR Lab.

15. 감사합니다.