Active Record Autosave Association
AutosaveAssociation
is a module that takes care of automatically saving associated 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 then new association records are saved but the updated association records are not saved.
Validation
Child records are validated unless :validate
is false
.
Callbacks
Association with autosave option defines several callbacks on your model (around_save, before_save, after_create, after_update). Please note that callbacks are executed in the order they were defined in model. You should avoid modifying the association content before autosave callbacks are executed. Placing your callbacks after associations is usually a good practice.
One-to-one Example
class Post < ActiveRecord::Base
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 < ActiveRecord::Base
has_many :comments # :autosave option is not 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')
comment = post.comments.create(body: 'hello world')
comment.body = 'hi everyone'
post.save # => saves post, but not comment
When :autosave
is true all children are saved, no matter whether they are new records or not:
class Post < ActiveRecord::Base
has_many :comments, autosave: true
end
post = Post.create(title: 'ruby rocks')
comment = post.comments.create(body: 'hello world')
comment.body = 'hi everyone'
post.comments.build(body: "good morning.")
post.save # => saves post and both comments.
Destroying one of the associated models as part of the parent’s save action is as simple as marking it for destruction:
post.comments # => [#<Comment id: 1, ...>, #<Comment id: 2, ...]>
post.comments[1].mark_for_destruction
post.comments[1].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
Caveats
Note that autosave will only trigger for already-persisted association records if the records themselves have been changed. This is to protect against SystemStackError
caused by circular association validations. The one exception is if a custom validation context is used, in which case the validations will always fire on the associated records.
- C
- D
- M
- R
Instance Public methods
changed_for_autosave?() Link
Returns whether or not this record has been changed in any way (including whether any of its nested autosave associations are likewise changed)
destroyed_by_association() Link
Returns the association for the parent being destroyed.
Used to avoid updating the counter cache unnecessarily.
destroyed_by_association=(reflection) Link
Records the association that is being destroyed and destroying this record in the process.
mark_for_destruction() Link
Marks this record to be destroyed as part of the parent’s save transaction. This does not actually destroy the record instantly, rather child record will be destroyed when parent.save
is called.
Only useful if the :autosave
option on the parent is enabled for this associated model.
marked_for_destruction?() Link
Returns whether or not this record will be destroyed as part of the parent’s save transaction.
Only useful if the :autosave
option on the parent is enabled for this associated model.
reload(options = nil) Link
Reloads the attributes of the object as usual and clears marked_for_destruction
flag.