Ruby / Rails实例变量不在对象中

Question

I've recently forayed into Ruby (on Rails), and now I'm stuck.

I've created a class called Habit in habit.rb , shown below.

require 'date'

class Habit < ActiveRecord::Base
  attr_reader :created_at, :start
  attr_accessor :name, :record

  belongs_to :user

  after_initialize do
    @name = name
    @record = []
    @start = Date.today.yday()
    @created_at = Time.now()
  end
end

Steps to reproduce issue (in rails console --sandbox ):

1. star_monkey = Habit.create(name: "draw star")
2. star_monkey

This returns #<Habit id: 1, name: nil, days: nil, start: nil, created_at: nil, updated_at: "2013-10-14 21:32:35"> .

However, when I explicitly request an instance variable, like @name , @record , or @start , the proper values are returned.

star_monkey.name # returns "draw star"
star_monkey.record # returns []
star_monkey.start # returns 287

My question is: How is it that star_monkey.#{variable} is the correct value, but the record doesn't 'save' the proper value? And secondly, how would I remedy this?

Answer 1

In the console you are using the create method which automatically saves the new object with the values provided to it. If you use new , then it will not save the object. If you want to check, try to see the id of the object while using create and new method. You will see the difference. When you use create it will automatically get saved with id in it but when you use new it will not save unless you use object.save . Thanks

Answer 2

由于某种原因，使用下面的设置属性起作用。

self[:attribute] = "value"