has_one association may silently drop associated record when it is invalid

This is quite an edge case, and appears like a bug in Rails (4.2.6) to me.

Update: This is now documented on Edgeguides Ruby on Rails Show archive.org snapshot :

If you set the :validate option to true, then associated objects will be validated whenever you save this object. By default, this is false: associated objects will not be validated when this object is saved.

Setup

# post.rb
class Post < ActiveRecord::Base
  has_one :attachment
end

# attachment.rb
class Attachment < ActiveRecord::Base
  belongs_to :post
  validates :title, presence: true
end

Issue

When creating a post with an invalid attachment, I expect the creation to fail because of attachment validation errors. However, the attachment is silently not stored to the database.

post = Post.create!(attachment: Attachment.new)
post.id # => 123
post.attachment.id # => nil

This only happens …

when relying on autosave. Explicitly setting autosave: true fixes this. Also, adding validate: true to has_one :attachment fixes this.
with has_one. When it's has_many :attachments, validation errors of the attachment properly cancel the creation of the post.
when creating both post and attachment at the same time. Updating an already persisted post with an invalid attachment cancels the update.

Dominik Schöler

makandra.de

Say thanks3

Last edit

2019-07-18

Emanuel

License

Source code in this card is licensed under the MIT License.

Rails: When to use :inverse_of in has_many, has_one or belongs_to associations

When you have two models in a has_many, has_one or belongs_to association, the :inverse_of option in Rails tells ActiveRecord that they're two sides of the same association.

Example with a has_many / belongs_to association:

c...

Cucumber may complain about cucumber.yml being invalid when it is valid

Running Cucumber tests while your cucumber.yml is 100% valid may still produce the following error.

cucumber.yml was found, but could not be parsed. Please refer to cucumber's documentation on correct profile usage.

This may in fact be d...

Machinist's #make breaks on has_many associations when defining method `empty?`

Observed on Rails 2.3 and machinist 1.0.6

Like the title says, when you define the method empty? like in the following example, you may not longer use collection.make.

class Book

  has_many :pages

  def empty?
    pages...

Careful when writing to has_many :through associations

tl;dr: Using has_many associations with a :through option can lead to lost or duplicate records. You should avoid them, or only use them to read records.

Consider this:

class User < ActiveRecord::Base
end

class Party < Activ...

Bugfix: Rails 2 does not find an association when it is named with a string instead of a symbol

Association named 'variations' was not found; perhaps you misspelled it?

I just was hunting down a strange error with this model:

class Model
  placeholder = 'variations'
  
  has_many placeholder
  
  nested_scope :v...

Don't forget: Automatically remove join records on has_many :through associations

Bad

# Given the following models

class Image < ActiveRecord::Base
  has_many :album_images
  has_many :albums, through: :album_images
end

class Album < ActiveRecord::Base
  has_many :album_images
  has_many :images, through: :album_i...

Posted by Dominik Schöler to makandra dev (2016-07-13 07:17)

has_one association may silently drop associated record when it is invalid

Setup

Issue

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