Agile Web Development Using Rails 6/

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Organizing Structures

Organizing Structures

Get familiar with Ruby's classes and modules

We'll cover the following...

Ruby has two basic concepts for organizing methods: classes and modules. We will cover each in turn.

Classes

Here’s a Ruby class definition:

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class Order < ApplicationRecord 
  has_many :line_items
  def self.find_all_unpaid
    self.where('paid = 0') 
  end
  def total
    sum = 0
    line_items.each {|li| sum += li.total} 
    sum
  end 
end

Class definitions start with the class keyword, followed by the class name (which must start with an uppercase letter). This Order class is defined as a subclass of the ApplicationRecord class.

Rails makes heavy use of class-level declarations. Here, has_many in line 2 is a method that’s defined by Active Record. It’s called “The definition of Order class”. Normally these kinds of methods make assertions about the class, so in this course we will call them declarations.

Within a class body, we can define class methods and instance methods. ...