Getting changed data from Model - Active Record 5/ Rails

Question

I am using Active record 5 in my custom Ruby script.

(Controller/Rake task)

books.each do |book|
  b_id = book[“b_id”]
  bk = Books.where(book_id: b_id).first
  bk = Books.new(book_id: b_id) unless bk
  bk.update_book_info(book)
  if bk.changed?
    # ...send book title to Api...
    bk.save! 
  end
end

(Model)

class Book < ActiveRecord::Base
  before_save :get_title
  def update_book_info(book)
    @book = book
  end

  private
  def  get_title
    # do ..something
    self.title = @book[’title’]
  end

 end

books is an array.

Please note the [...send book title to Api...] part. I need to know the book title so that I can send it to API. I have tried bk.title but it returns null !

How to get the book title ?

Also, can I move more code from controller to model?

Help :)

Answer 1

If it returns nil ... Then it is empty. Check the object in your rails console. In your terminal, run:

rails c

Then:

Book.first # see the whole object
Book.first.title # see its title
Book.all.pluck(:title) # see all the titles in the database

You might want to check where you save your books if there isn't something wrong which would cause the title not to be saved.

Side note: in your code, you're doing some unnecessary queries. In your each loop, you're querying the database for an object your already have. This line:

bk = Books.where(book_id: b_id).first # useless query

Is going to return the same book object from which you extracted the id . Also, when looking for an object with an id, no need to use where since an id is unique, it can only return one object. Use #find or #find_by .

Answer 2

Instead create the method #update_book_info you could use #assign_attributes(new_attributes) like this:

bk.assign_attributes(book)

It will guarantee that your model will be dirt and the #changed? method will work. Also, your bk#title will be loaded before the #save , which seems to be what you want.

Then you will be able to remove the before_save and #get_title as well.