ActiveStorage with Rails API

[NicholasLYang]

I'm basically trying to get ActiveStorage working with Rails API. The main issue I have is getting a URL from an Attachment object. url_for doesn't work outside of Rails views, so I cannot get the url from that. In addition, I'm not quite clear on creating an article with an image. The following code when run in the Rails console does not create an attachment:

School.create(name: "New York University", image: File.open(Rails.root + "db/sample.jpg"))

Instead, it simply gives the following:

(0.1ms)  begin transaction
  School Create (0.8ms)  INSERT INTO "schools" ("name", "created_at", "updated_at") VALUES (?, ?, ?)  [["name", "New York University"], ["created_at", "2018-04-09 03:36:54.304927"], ["updated_at", "2018-04-09 03:36:54.304927"]]
   (2.8ms)  commit transaction
=> #<School id: 4, name: "New York University", created_at: "2018-04-09 03:36:54", updated_at: "2018-04-09 03:36:54">

Steps to reproduce

Try to run url_for in the Rails console.

Expected behavior

I get the url. Granted, I get that this is not the purpose of url_for (it's a view helper, not a method). But I'd like some equivalent, ideally a method in the ActiveStorage::Attached object.

Actual behavior

url_for gives the following error: (undefined method 'url_for' for main:Object). Even when I include the Rails view helpers, I get the following:

ArgumentError (Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true)

I could try adding a host to the ActiveStorage::Attached object, but that's sorta hackneyed as splats don't work with it, and I can't mutate it easily.

System configuration

Rails version:
5.2.0.rc2
Ruby version:
ruby 2.5.0p0

Thank you for your time. I understand that ActiveStorage is not fully stable or released yet, but it looked too damn cool to not use 😄 . I'd be open to contributing/opening a PR if someone could point me in the right direction.

[saurabhbhatia]

Hi @NicholasLYang I've been using @model.attachment.service_url in my serializers to get the path of the image, but it has it's limitations. service_url is generated fresh with every request. I would also like to know a better solution( if there is) for getting the image display url that we can pass through our serializers to the frontend.

[pixeltrix]

Active Storage provides rails_blob_path and rails_blob_url url helpers that provide a permanent link to a blob. These permanent links are signed and will redirect to a service url so for example the S3 service url will be a presigned temporary url. Note that the urls are public and if you need to make them protected you'll need to create your own version of ActiveStorage::BlobsController.

For further information I suggest reading the beta guide for Active Storage.

[NicholasLYang]

Hey @pixeltrix, I appreciate the response, but I'm still a little confused on link generation. For instance, if I'm creating a variant, I get the following error: NoMethodError (undefined method 'signed_id' for #<ActiveStorage::Variant:0x00007fb73590b5e8>), which appears to be due to the fact that variants are not the same as attachments. However, this seems rather awkward, as I can't use the same helper for variants and attachments (even though imo the interface should be pretty similar if not identical). Furthermore, I just bumped my Rails version to 5.2.0 and now the solution I was using for variants, @model.attachment.variant(resize: "100x100>").processed.service_url, gives a host error. Could you clarify the link generation process for variants vs attachments and why they're different? I get that variants need to be generated lazily but I'm not quite clear on the entire picture.

[saurabhbhatia]

@NicholasLYang this is what is working for me ( I upgraded to Rails 5.2 this morning from RC2 ).

class API::V1::ProfileSerializer < ActiveModel::Serializer
  include Rails.application.routes.url_helpers
  attributes :id, :name, :avatar_url

  def avatar_url
    rails_blob_path(object.avatar) if object.avatar.attachment
  end
end

This is how my development.rb looks like

  config.action_mailer.default_url_options = { host: 'test.com' }
  Rails.application.routes.default_url_options[:host] = 'test.com'

[pixeltrix]

@NicholasLYang for a variant you need to use rails_representation_url(variant) - this will build a url similar to the one that rails_blob_url builds but specifically for that variant. Don't use service_url directly within things like model serializers as it's generally a temporary url. The idea is to use permanent urls that are independent of the service that redirect to the temporary service url so that you can migrate to a different service without affecting end users.

[PrimeTimeTran]

@pixeltrix thanks for the work you've put in so far. Anyway you guys could add documentation to the guides for working with AWS? I'm having the same error message when I use ActiveModelSerializers and AWS S3 to host the media files.

[PrimeTimeTran]

@saurabhbhatia are you hosting your images on the same server? I keep getting the same error message and I think it has to do with using AWS instead of saving the images to the application

[philiplambok]

I have the same problem too,

When im using service_url and processed.service_url (in variant), its working in production but error in development. It's still error when i add code in config.

# config/development.rb
config.active_storage.service = :local
config.default_url_options = { host: "localhost:3000" }
config.action_mailer.default_url_options = { :host => "localhost:3000" }

#config/production.rb
config.active_storage.service = :amazon
config.action_mailer.default_url_options = { host: 'https://kappuchino.herokuapp.com' }
config.default_url_options = { host: "https://kappuchino.herokuapp.com" }

And if i am use rails_blob_url its working in development, but in production it doesn't work its return link localhost.

[philiplambok]

Oh i just fixed the problem,

i'm using method rails_blob_path and rails_representation_path(for variant). rails_blob_url and rails_representation_url don't work for me.

[LuisHCK]

if you are using fast_jsonapi serializer this may work

attribute :cover do |object| 
  Rails.application.routes.url_helpers.rails_blob_url(object.cover) if object.cover.attached?
end

and add this in any initializer
Rails.application.routes.default_url_options[:host] = 'localhost:3000'

[madmatvey]

if you need service_url only method, you can write callback at your controller to handle service_url method at development and test environments.

class Api::V1::YourPerfectApiController < ApplicationController
    before_action :set_host_for_local_storage
    ...
    private
     def set_host_for_local_storage
        ActiveStorage::Current.host = request.base_url if Rails.application.config.active_storage.service == :local
    end
end

see ActiveStorage controllers concerns

[TienNT1993]

@madmatvey Thank you so much, it made my day!

[belgoros]

When using the settings suggested by @philiplambok, it fails as follows:

Completed 500 Internal Server Error in 277ms (ActiveRecord: 8.7ms)
ArgumentError (Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true):

rails: 5.2.0

In development.rb:

...
config.active_storage.service = :local
config.default_url_options = { host: "localhost:3000" }

What am I missing ?

[belgoros]

Finally the option that worked for me was:

#development.rb

Rails.application.routes.default_url_options[:host] = 'localhost:3000'

And in my serialiser I used:

#post_serializer.rb
class PostSerializer < ActiveModel::Serializer
  include Rails.application.routes.url_helpers

  attributes :id, :title, :body, :tag_ids, :archived, :photo

  def photo
    rails_blob_url(object.photo) if object.photo.attached?
  end
end

The code source of the app is here.