Delete alternatively takes a model

lib/guacamole/collection.rb

@@ -115,13 +115,20 @@ def save(model)
         model
       end
 
-      # Delete a model from the database by key
+      # Delete a model from the database
       #
-      # @param [String] key The key of the model
+      # @param [String, Model] model_or_key The key of the model or a model
       # @return [String] The key
-      # @example Delete a podcast
+      # @example Delete a podcast by key
       #   PodcastsCollection.delete(podcast.key)
-      def delete(key)
+      # @example Delete a podcast by model
+      #   PodcastsCollection.delete(podcast)
+      def delete(model_or_key)
+        key = if model_or_key.respond_to? :key
+          model_or_key.key
+        else
+          model_or_key
+        end
         fetch_document(key).delete
         key
       end

spec/unit/collection_spec.rb

@@ -197,20 +197,35 @@ class TestCollection
   describe 'delete' do
     let(:document) { double('Document') }
     let(:key)      { double('Key') }
+    let(:model)    { double('Model', key: key) }
 
     before do
       allow(connection).to receive(:fetch).with(key).and_return(document)
       allow(document).to receive(:delete)
     end
 
-    it 'should delete the according document' do
-      expect(document).to receive(:delete)
+    context 'a key was provided' do
+      it 'should delete the according document' do
+        expect(document).to receive(:delete)
 
-      subject.delete key
+        subject.delete key
+      end
+
+      it 'should return the according key' do
+        expect(subject.delete(key)).to eq key
+      end
     end
 
-    it 'should return the according key' do
-      expect(subject.delete(key)).to eq key
+    context 'a model was provided' do
+      it 'should delete the according document' do
+        expect(document).to receive(:delete)
+
+        subject.delete model
+      end
+
+      it 'should return the according key' do
+        expect(subject.delete(model)).to eq key
+      end
     end
   end