Active Record Autosave Association
AutosaveAssociation is a module that takes care of automatically
saving associacted records when their parent is saved. In addition to
saving, it also destroys any associated records that were marked for
destruction. (See mark_for_destruction
and marked_for_destruction?).
Saving of the parent, its associations, and the destruction of marked
associations, all happen inside a transaction. This should never leave the
database in an inconsistent state.
If validations for any of the associations fail, their error messages will
be applied to the parent.
Note that it also means that associations marked for destruction
won’t be destroyed directly. They will however still be marked for
destruction.
Note that :autosave => false is not same as not declaring
:autosave. When the :autosave option is not present new
associations are saved.
One-to-one Example
class Post
has_one :author, :autosave => true
end
Saving changes to the parent and its associated model can now be performed
automatically and atomically:
post = Post.find(1)
post.title # => "The current global position of migrating ducks"
post.author.name # => "alloy"
post.title = "On the migration of ducks"
post.author.name = "Eloy Duran"
post.save
post.reload
post.title # => "On the migration of ducks"
post.author.name # => "Eloy Duran"
Destroying an associated model, as part of the parent’s save action,
is as simple as marking it for destruction:
post.author.mark_for_destruction
post.author.marked_for_destruction? # => true
Note that the model is not yet removed from the database:
id = post.author.id
Author.find_by_id(id).nil? # => false
post.save
post.reload.author # => nil
Now it is removed from the database:
Author.find_by_id(id).nil? # => true
One-to-many Example
When :autosave is not declared new children are saved when their
parent is saved:
class Post
has_many :comments # :autosave option is no declared
end
post = Post.new(:title => 'ruby rocks')
post.comments.build(:body => 'hello world')
post.save # => saves both post and comment
post = Post.create(:title => 'ruby rocks')
post.comments.build(:body => 'hello world')
post.save # => saves both post and comment
post = Post.create(:title => 'ruby rocks')
post.comments.create(:body => 'hello world')
post.save # => saves both post and comment
When :autosave is true all children is saved, no matter whether
they are new records:
class Post
has_many :comments, :autosave => true
end
post = Post.create(:title => 'ruby rocks')
post.comments.create(:body => 'hello world')
post.comments[0].body = 'hi everyone'
post.save # => saves both post and comment, with 'hi everyone' as title
Destroying one of the associated models as part of the parent’s save
action is as simple as marking it for destruction:
post.comments.last.mark_for_destruction
post.comments.last.marked_for_destruction? # => true
post.comments.length # => 2
Note that the model is not yet removed from the database:
id = post.comments.last.id
Comment.find_by_id(id).nil? # => false
post.save
post.reload.comments.length # => 1
Now it is removed from the database:
Comment.find_by_id(id).nil? # => true
Validation
Children records are validated unless :validate is false.
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