Extract Analyzable and Representable concerns

activestorage/app/models/active_storage/blob.rb

 # frozen_string_literal: true
 
-require "active_storage/analyzer/null_analyzer"
-
 # A blob is a record that contains the metadata about a file and a key for where that file resides on the service.
 # Blobs can be created in two ways:
 #
@@ -16,9 +14,7 @@
 # update a blob's metadata on a subsequent pass, but you should not update the key or change the uploaded file.
 # If you need to create a derivative or otherwise change the blob, simply create a new blob and purge the old one.
 class ActiveStorage::Blob < ActiveRecord::Base
-  class InvariableError < StandardError; end
-  class UnpreviewableError < StandardError; end
-  class UnrepresentableError < StandardError; end
+  include Analyzable, Representable
 
   self.table_name = "active_storage_blobs"
 
@@ -29,8 +25,6 @@ class UnrepresentableError < StandardError; end
 
   has_many :attachments
 
-  has_one_attached :preview_image
-
   class << self
     # You can used the signed ID of a blob to refer to it on the client side without fear of tampering.
     # This is particularly helpful for direct uploads where the client-side needs to refer to the blob
@@ -69,7 +63,6 @@ def create_before_direct_upload!(filename:, byte_size:, checksum:, content_type:
     end
   end
 
-
   # Returns a signed ID for this blob that's suitable for reference on the client-side without fear of tampering.
   # It uses the framework-wide verifier on <tt>ActiveStorage.verifier</tt>, but with a dedicated purpose.
   def signed_id
@@ -112,91 +105,6 @@ def text?
   end
 
 
-  # Returns an ActiveStorage::Variant instance with the set of +transformations+ provided. This is only relevant for image
-  # files, and it allows any image to be transformed for size, colors, and the like. Example:
-  #
-  #   avatar.variant(resize: "100x100").processed.service_url
-  #
-  # This will create and process a variant of the avatar blob that's constrained to a height and width of 100px.
-  # Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
-  #
-  # Frequently, though, you don't actually want to transform the variant right away. But rather simply refer to a
-  # specific variant that can be created by a controller on-demand. Like so:
-  #
-  #   <%= image_tag Current.user.avatar.variant(resize: "100x100") %>
-  #
-  # This will create a URL for that specific blob with that specific variant, which the ActiveStorage::VariantsController
-  # can then produce on-demand.
-  #
-  # Raises ActiveStorage::Blob::InvariableError if ImageMagick cannot transform the blob. To determine whether a blob is
-  # variable, call ActiveStorage::Blob#previewable?.
-  def variant(transformations)
-    if variable?
-      ActiveStorage::Variant.new(self, ActiveStorage::Variation.wrap(transformations))
-    else
-      raise InvariableError
-    end
-  end
-
-  # Returns true if ImageMagick can transform the blob (its content type is in +ActiveStorage.variable_content_types+).
-  def variable?
-    ActiveStorage.variable_content_types.include?(content_type)
-  end
-
-
-  # Returns an ActiveStorage::Preview instance with the set of +transformations+ provided. A preview is an image generated
-  # from a non-image blob. Active Storage comes with built-in previewers for videos and PDF documents. The video previewer
-  # extracts the first frame from a video and the PDF previewer extracts the first page from a PDF document.
-  #
-  #   blob.preview(resize: "100x100").processed.service_url
-  #
-  # Avoid processing previews synchronously in views. Instead, link to a controller action that processes them on demand.
-  # Active Storage provides one, but you may want to create your own (for example, if you need authentication). Here’s
-  # how to use the built-in version:
-  #
-  #   <%= image_tag video.preview(resize: "100x100") %>
-  #
-  # This method raises ActiveStorage::Blob::UnpreviewableError if no previewer accepts the receiving blob. To determine
-  # whether a blob is accepted by any previewer, call ActiveStorage::Blob#previewable?.
-  def preview(transformations)
-    if previewable?
-      ActiveStorage::Preview.new(self, ActiveStorage::Variation.wrap(transformations))
-    else
-      raise UnpreviewableError
-    end
-  end
-
-  # Returns true if any registered previewer accepts the blob. By default, this will return true for videos and PDF documents.
-  def previewable?
-    ActiveStorage.previewers.any? { |klass| klass.accept?(self) }
-  end
-
-
-  # Returns an ActiveStorage::Preview for a previewable blob or an ActiveStorage::Variant for a variable image blob.
-  #
-  #   blob.representation(resize: "100x100").processed.service_url
-  #
-  # Raises ActiveStorage::Blob::UnrepresentableError if the receiving blob is neither variable nor previewable. Call
-  # ActiveStorage::Blob#representable? to determine whether a blob is representable.
-  #
-  # See ActiveStorage::Blob#preview and ActiveStorage::Blob#variant for more information.
-  def representation(transformations)
-    case
-    when previewable?
-      preview transformations
-    when variable?
-      variant transformations
-    else
-      raise UnrepresentableError
-    end
-  end
-
-  # Returns true if the blob is variable or previewable.
-  def representable?
-    variable? || previewable?
-  end
-
-
   # Returns the URL of the blob on the service. This URL is intended to be short-lived for security and not used directly
   # with users. Instead, the +service_url+ should only be exposed as a redirect from a stable, possibly authenticated URL.
   # Hiding the +service_url+ behind a redirect also gives you the power to change services without updating all URLs. And
@@ -216,6 +124,7 @@ def service_headers_for_direct_upload
     service.headers_for_direct_upload key, filename: filename, content_type: content_type, content_length: byte_size, checksum: checksum
   end
 
+
   # Uploads the +io+ to the service on the +key+ for this blob. Blobs are intended to be immutable, so you shouldn't be
   # using this method after a file has already been uploaded to fit with a blob. If you want to create a derivative blob,
   # you should instead simply create a new blob based on the old one.
@@ -240,46 +149,6 @@ def download(&block)
   end
 
 
-  # Extracts and stores metadata from the file associated with this blob using a relevant analyzer. Active Storage comes
-  # with built-in analyzers for images and videos. See ActiveStorage::Analyzer::ImageAnalyzer and
-  # ActiveStorage::Analyzer::VideoAnalyzer for information about the specific attributes they extract and the third-party
-  # libraries they require.
-  #
-  # To choose the analyzer for a blob, Active Storage calls +accept?+ on each registered analyzer in order. It uses the
-  # first analyzer for which +accept?+ returns true when given the blob. If no registered analyzer accepts the blob, no
-  # metadata is extracted from it.
-  #
-  # In a Rails application, add or remove analyzers by manipulating +Rails.application.config.active_storage.analyzers+
-  # in an initializer:
-  #
-  #   # Add a custom analyzer for Microsoft Office documents:
-  #   Rails.application.config.active_storage.analyzers.append DOCXAnalyzer
-  #
-  #   # Remove the built-in video analyzer:
-  #   Rails.application.config.active_storage.analyzers.delete ActiveStorage::Analyzer::VideoAnalyzer
-  #
-  # Outside of a Rails application, manipulate +ActiveStorage.analyzers+ instead.
-  #
-  # You won't ordinarily need to call this method from a Rails application. New blobs are automatically and asynchronously
-  # analyzed via #analyze_later when they're attached for the first time.
-  def analyze
-    update! metadata: metadata.merge(extract_metadata_via_analyzer)
-  end
-
-  # Enqueues an ActiveStorage::AnalyzeJob which calls #analyze.
-  #
-  # This method is automatically called for a blob when it's attached for the first time. You can call it to analyze a blob
-  # again (e.g. if you add a new analyzer or modify an existing one).
-  def analyze_later
-    ActiveStorage::AnalyzeJob.perform_later(self)
-  end
-
-  # Returns true if the blob has been analyzed.
-  def analyzed?
-    analyzed
-  end
-
-
   # Deletes the file on the service that's associated with this blob. This should only be done if the blob is going to be
   # deleted as well or you will essentially have a dead reference. It's recommended to use the +#purge+ and +#purge_later+
   # methods in most circumstances.
@@ -313,20 +182,6 @@ def compute_checksum_in_chunks(io)
       end.base64digest
     end
 
-
-    def extract_metadata_via_analyzer
-      analyzer.metadata.merge(analyzed: true)
-    end
-
-    def analyzer
-      analyzer_class.new(self)
-    end
-
-    def analyzer_class
-      ActiveStorage.analyzers.detect { |klass| klass.accept?(self) } || ActiveStorage::Analyzer::NullAnalyzer
-    end
-
-
     def forcibly_serve_as_binary?
       ActiveStorage.content_types_to_serve_as_binary.include?(content_type)
     end

activestorage/app/models/active_storage/blob/analyzable.rb

+require "active_storage/analyzer/null_analyzer"
+
+module ActiveStorage::Blob::Analyzable
+  # Extracts and stores metadata from the file associated with this blob using a relevant analyzer. Active Storage comes
+  # with built-in analyzers for images and videos. See ActiveStorage::Analyzer::ImageAnalyzer and
+  # ActiveStorage::Analyzer::VideoAnalyzer for information about the specific attributes they extract and the third-party
+  # libraries they require.
+  #
+  # To choose the analyzer for a blob, Active Storage calls +accept?+ on each registered analyzer in order. It uses the
+  # first analyzer for which +accept?+ returns true when given the blob. If no registered analyzer accepts the blob, no
+  # metadata is extracted from it.
+  #
+  # In a Rails application, add or remove analyzers by manipulating +Rails.application.config.active_storage.analyzers+
+  # in an initializer:
+  #
+  #   # Add a custom analyzer for Microsoft Office documents:
+  #   Rails.application.config.active_storage.analyzers.append DOCXAnalyzer
+  #
+  #   # Remove the built-in video analyzer:
+  #   Rails.application.config.active_storage.analyzers.delete ActiveStorage::Analyzer::VideoAnalyzer
+  #
+  # Outside of a Rails application, manipulate +ActiveStorage.analyzers+ instead.
+  #
+  # You won't ordinarily need to call this method from a Rails application. New blobs are automatically and asynchronously
+  # analyzed via #analyze_later when they're attached for the first time.
+  def analyze
+    update! metadata: metadata.merge(extract_metadata_via_analyzer)
+  end
+
+  # Enqueues an ActiveStorage::AnalyzeJob which calls #analyze.
+  #
+  # This method is automatically called for a blob when it's attached for the first time. You can call it to analyze a blob
+  # again (e.g. if you add a new analyzer or modify an existing one).
+  def analyze_later
+    ActiveStorage::AnalyzeJob.perform_later(self)
+  end
+
+  # Returns true if the blob has been analyzed.
+  def analyzed?
+    analyzed
+  end
+
+  private
+    def extract_metadata_via_analyzer
+      analyzer.metadata.merge(analyzed: true)
+    end
+
+    def analyzer
+      analyzer_class.new(self)
+    end
+
+    def analyzer_class
+      ActiveStorage.analyzers.detect { |klass| klass.accept?(self) } || ActiveStorage::Analyzer::NullAnalyzer
+    end
+end

activestorage/app/models/active_storage/blob/representable.rb

+module ActiveStorage::Blob::Representable
+  extend ActiveSupport::Concern
+
+  included do
+    has_one_attached :preview_image
+  end
+
+  # Returns an ActiveStorage::Variant instance with the set of +transformations+ provided. This is only relevant for image
+  # files, and it allows any image to be transformed for size, colors, and the like. Example:
+  #
+  #   avatar.variant(resize: "100x100").processed.service_url
+  #
+  # This will create and process a variant of the avatar blob that's constrained to a height and width of 100px.
+  # Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
+  #
+  # Frequently, though, you don't actually want to transform the variant right away. But rather simply refer to a
+  # specific variant that can be created by a controller on-demand. Like so:
+  #
+  #   <%= image_tag Current.user.avatar.variant(resize: "100x100") %>
+  #
+  # This will create a URL for that specific blob with that specific variant, which the ActiveStorage::VariantsController
+  # can then produce on-demand.
+  #
+  # Raises ActiveStorage::Blob::InvariableError if ImageMagick cannot transform the blob. To determine whether a blob is
+  # variable, call ActiveStorage::Blob#previewable?.
+  def variant(transformations)
+    if variable?
+      ActiveStorage::Variant.new(self, ActiveStorage::Variation.wrap(transformations))
+    else
+      raise ActiveStorage::InvariableError
+    end
+  end
+
+  # Returns true if ImageMagick can transform the blob (its content type is in +ActiveStorage.variable_content_types+).
+  def variable?
+    ActiveStorage.variable_content_types.include?(content_type)
+  end
+
+
+  # Returns an ActiveStorage::Preview instance with the set of +transformations+ provided. A preview is an image generated
+  # from a non-image blob. Active Storage comes with built-in previewers for videos and PDF documents. The video previewer
+  # extracts the first frame from a video and the PDF previewer extracts the first page from a PDF document.
+  #
+  #   blob.preview(resize: "100x100").processed.service_url
+  #
+  # Avoid processing previews synchronously in views. Instead, link to a controller action that processes them on demand.
+  # Active Storage provides one, but you may want to create your own (for example, if you need authentication). Here’s
+  # how to use the built-in version:
+  #
+  #   <%= image_tag video.preview(resize: "100x100") %>
+  #
+  # This method raises ActiveStorage::Blob::UnpreviewableError if no previewer accepts the receiving blob. To determine
+  # whether a blob is accepted by any previewer, call ActiveStorage::Blob#previewable?.
+  def preview(transformations)
+    if previewable?
+      ActiveStorage::Preview.new(self, ActiveStorage::Variation.wrap(transformations))
+    else
+      raise ActiveStorage::UnpreviewableError
+    end
+  end
+
+  # Returns true if any registered previewer accepts the blob. By default, this will return true for videos and PDF documents.
+  def previewable?
+    ActiveStorage.previewers.any? { |klass| klass.accept?(self) }
+  end
+
+
+  # Returns an ActiveStorage::Preview for a previewable blob or an ActiveStorage::Variant for a variable image blob.
+  #
+  #   blob.representation(resize: "100x100").processed.service_url
+  #
+  # Raises ActiveStorage::Blob::UnrepresentableError if the receiving blob is neither variable nor previewable. Call
+  # ActiveStorage::Blob#representable? to determine whether a blob is representable.
+  #
+  # See ActiveStorage::Blob#preview and ActiveStorage::Blob#variant for more information.
+  def representation(transformations)
+    case
+    when previewable?
+      preview transformations
+    when variable?
+      variant transformations
+    else
+      raise ActiveStorage::UnrepresentableError
+    end
+  end
+
+  # Returns true if the blob is variable or previewable.
+  def representable?
+    variable? || previewable?
+  end
+end

activestorage/lib/active_storage.rb

@@ -26,7 +26,9 @@
 require "active_record"
 require "active_support"
 require "active_support/rails"
+
 require "active_storage/version"
+require "active_storage/errors"
 
 module ActiveStorage
   extend ActiveSupport::Autoload

activestorage/lib/active_storage/errors.rb

+module ActiveStorage
+  class InvariableError < StandardError; end
+  class UnpreviewableError < StandardError; end
+  class UnrepresentableError < StandardError; end
+end

activestorage/test/models/preview_test.rb

@@ -33,7 +33,7 @@ class ActiveStorage::PreviewTest < ActiveSupport::TestCase
   test "previewing an unpreviewable blob" do
     blob = create_file_blob
 
-    assert_raises ActiveStorage::Blob::UnpreviewableError do
+    assert_raises ActiveStorage::UnpreviewableError do
       blob.preview resize: "640x280"
     end
   end

activestorage/test/models/representation_test.rb

@@ -34,7 +34,7 @@ class ActiveStorage::RepresentationTest < ActiveSupport::TestCase
   test "representing an unrepresentable blob" do
     blob = create_blob
 
-    assert_raises ActiveStorage::Blob::UnrepresentableError do
+    assert_raises ActiveStorage::UnrepresentableError do
       blob.representation resize: "100x100"
     end
   end

activestorage/test/models/variant_test.rb

@@ -59,7 +59,7 @@ class ActiveStorage::VariantTest < ActiveSupport::TestCase
   end
 
   test "variation of invariable blob" do
-    assert_raises ActiveStorage::Blob::InvariableError do
+    assert_raises ActiveStorage::InvariableError do
       create_file_blob(filename: "report.pdf", content_type: "application/pdf").variant(resize: "100x100")
     end
   end