How to update attachment in ActiveStorage (Rails 5.2)
I have the same problem the with image saving. I hope this will help
class User < ApplicationRecord
has_one_attached :avatar
end
let look at the form and controller
= simple_form_for(@user) do |f|
= f.error_notification
.form-inputs
= f.input :name
= f.input :email
= f.input :avatar, as: :file
.form-actions
= f.button :submit
controllers/posts_controller.rb
def create
@user = User.new(post_params)
@user.avatar.attach(params[:post][:avatar])
respond_to do |format|
if @user.save
format.html { redirect_to @user, notice: 'Post was successfully created.' }
format.json { render :show, status: :created, location: @user }
else
format.html { render :new }
format.json { render json: @user.errors, status: :unprocessable_entity }
end
end
end
The cause of the error
This error is being raised by the has_one
association between your model and the attachment record. It occurs because trying to replace the original attachment with a new one will orphan the original and cause it to fail the foreign key constraint for belongs_to
associations. This is the behavior for all ActiveRecord has_one
relationships (i.e. it’s not specific to ActiveStorage).
An analogous example
class User < ActiveRecord::Base
has_one :profile
end
class Profile < ActiveRecord::Base
belongs_to :user
end
# create a new user record
user = User.create!
# create a new associated profile record (has_one)
original_profile = user.create_profile!
# attempt to replace the original profile with a new one
user.create_profile!
=> ActiveRecord::RecordNotSaved: Failed to remove the existing associated profile. The record failed to save after its foreign key was set to nil.
In attempting to create a new profile, ActiveRecord tries to set the user_id
of the original profile to nil
, which fails the foreign key constraint for belongs_to
records. I believe this is essentially what is happening when you try and attach a new file to your model using ActiveStorage... doing so tries to nullify the foreign key of the original attachment record, which will fail.
The solution
The solution for has_one
relationships is to destroy the associated record before trying to create a new one (i.e. purging the attachment before trying to attach another one).
user.avatar.purge # or user.avatar.purge_later
user.avatar.attach(params[:file])
Is this desired behavior?
Whether or not ActiveStorage should automatically purge the original record when trying to attach a new one for has_one relationships is a different question best posed to the core team...
IMO having it work consistently with all other has_one relationships makes sense, and it may be preferable to leave it up to the developer to be explicit about purging an original record before attaching a new one rather than doing it automatically (which may be a bit presumptuous).
Resources:
- Source code for
has_one
error raising behavior - Test case for
has_one
error raising behavior
You can call purge_later
before attach
when using has_one_attached
:
user.avatar.purge_later
user.avatar.attach(params[:file])
Update
Rails now purges previous attachment automatically (since Aug 29th).