Add keep-stored and reorder feature for multiple file uploader

README.md

@@ -190,6 +190,17 @@ u.avatars[0].current_path # => 'path/to/file.png'
 u.avatars[0].identifier # => 'file.png'
 ```
 
+If you want to preserve existing files on uploading new one, you can go like:
+
+```erb
+<% user.avatars.each do |avatar| %>
+  <%= hidden_field :user, :avatars, multiple: true, value: avatar.identifier %>
+<% end %>
+<%= form.file_field :avatars, multiple: true %>
+```
+
+Sorting avatars is supported as well by reordering `hidden_field`.
+
 ## Changing the storage directory
 
 In order to change where uploaded files are put, just override the `store_dir`

lib/carrierwave/mounter.rb

@@ -39,11 +39,16 @@ def uploaders
 
     def cache(new_files)
       return if new_files.blank?
+      old_uploaders = uploaders
       @uploaders = new_files.map do |new_file|
-        uploader = blank_uploader
-        uploader.cache!(new_file)
-        uploader
-      end
+        if new_file.is_a?(String)
+          old_uploaders.detect { |uploader| uploader.identifier == new_file }
+        else
+          uploader = blank_uploader
+          uploader.cache!(new_file)
+          uploader
+        end
+      end.compact
 
       @integrity_error = nil
       @processing_error = nil

spec/mount_multiple_spec.rb

@@ -236,6 +236,54 @@ def monkey
 
         it { expect(instance.images).to be_empty }
       end
+
+      describe "with stored files" do
+        before do
+          instance.images = [text_file_stub, test_file_stub]
+          instance.store_images!
+        end
+        let(:identifiers) { instance.images.map(&:identifier) }
+
+        it "preserves existing image of given identifier" do
+          instance.images = [identifiers[0], old_image_stub]
+          instance.store_images!
+          expect(instance.images.map(&:identifier)).to eq ['bork.txt','old.jpeg']
+        end
+
+        it "reorders existing image" do
+          instance.images = identifiers.reverse
+          instance.store_images!
+          expect(instance.images.map(&:identifier)).to eq ['test.jpg', 'bork.txt']
+        end
+
+        it "allows uploading and reordering at once" do
+          instance.images = [identifiers[1], old_image_stub, identifiers[0]]
+          instance.store_images!
+          expect(instance.images.map(&:identifier)).to eq ['test.jpg', 'old.jpeg', 'bork.txt']
+        end
+
+        it "allows repeating the same identifiers" do
+          instance.images = ['bork.txt', 'test.jpg', 'bork.txt']
+          instance.store_images!
+          expect(instance.images.map(&:identifier)).to eq ['bork.txt', 'test.jpg', 'bork.txt']
+        end
+
+        it "removes image which is unused" do
+          @image_paths = instance.images.map(&:current_path)
+          instance.images = [identifiers[0]]
+          instance.store_images!
+          instance.send(:_mounter, :images).remove_previous(identifiers, identifiers[0..0])
+          expect(instance.images.map(&:identifier)).to eq ['bork.txt']
+          expect(File.exist?(@image_paths[0])).to be_truthy
+          expect(File.exist?(@image_paths[1])).to be_falsey
+        end
+
+        it "ignores unknown identifier" do
+          instance.images = ['unknown.txt']
+          expect { instance.store_images! }.not_to raise_error
+          expect(instance.images.map(&:identifier)).to be_empty
+        end
+      end
     end
 
     describe '#images?' do