Save collection of updated records all at once

Question

As I understand it, the build method can be used to build up a collection of associated records before saving. Then, when calling save, all the chi

Answer 1

Firstly +1 to @andrea for Transactions - cool stuff I didn't know

But easiest way here to go is to use accepts_nested_attributes_for method for model.

Lets make an example. We have got two models: Post title:string and Comment body:string post:references

lets look into models:

class Post < ActiveRecord::Base
  has_many :comments
  validates :title, :presence => true
  accepts_nested_attributes_for :comments # this is our hero
end

class Comment < ActiveRecord::Base
  belongs_to :post
  validates :body, :presence => true
end

You see: we have got some validations here. So let's go to rails console to do some tests:

post = Post.new
post.save
#=> false
post.errors
#=> #["can't be blank"]}>
post.title = "My post title"
# now the interesting: adding association
# one comment is ok and second with __empty__ body
post.comments_attributes = [{:body => "My cooment"}, {:body => nil}]
post.save
#=> false
post.errors
#=> #["can't be blank"]}>
# Cool! everything works fine
# let's now cleean our comments and add some new valid
post.comments.destroy_all
post.comments_attributes = [{:body => "first comment"}, {:body => "second comment"}]
post.save
#=> true

Great! All works fine.

Now lets do the same things with update:

post = Post.last
post.comments.count # We have got already two comments with ID:1 and ID:2
#=> 2
# Lets change first comment's body
post.comments_attributes = [{:id => 1, :body => "Changed body"}] # second comment isn't changed
post.save
#=> true
# Now let's check validation
post.comments_attributes => [{:id => 1, :body => nil}]
post.save
#=> false
post.errors
#=> #["can't be blank"]}>

This works!

SO how can you use it. In your models the same way, and in views like common forms but with fields_for tag for association. Also you can use very deep nesting for your association with validations nd it will work perfect.