MONGOID-5910 Implement enumerable methods on top level models (any?, many?, and one?)

lib/mongoid/findable.rb

@@ -116,6 +116,36 @@ def exists?(id_or_conditions = :none)
       with_default_scope.exists?(id_or_conditions)
     end
 
+    # Return true if any documents exist in the criteria.
+    #
+    # @example Determine if any documents exist
+    #   criteria.any?
+    #   
+    # @return [ true | false ] If any documents exist.
+    def any?(*args, &block)
+      limit(1).count > 0
+    end
+
+    # Return true if only one document exists in the criteria.
+    #
+    # @example Determine if only one document exists
+    #   criteria.one?
+    #
+    # @return [ true | false ] If only one document exists.
+    def one?(*args, &block)
+      limit(2).count == 1
+    end
+
+    # Return true if more than one document exists in the criteria.
+    #
+    # @example Determine if many documents exist
+    #   criteria.many?
+    #
+    # @return [ true | false ] If many documents exist.
+    def many?(*args, &block)
+      limit(2).count > 1
+    end
+
     # Finds a +Document+ or multiple documents by their _id values.
     #
     # If a single non-Array argument is given, this argument is interpreted

spec/mongoid/criteria/findable_spec.rb

@@ -1302,6 +1302,201 @@
     end
   end
 
+  describe "#any?" do
+    context "when called on criteria" do
+      let!(:band) do
+        Band.create!(name: "Depeche Mode")
+      end
+
+      let!(:band_two) do
+        Band.create!(name: "Radiohead")
+      end
+
+      context "when documents exist" do
+
+        let(:criteria) do
+          Band.all
+        end
+
+        it "returns true" do
+          expect(criteria.any?).to be true
+        end
+      end
+
+      context "when no documents exist" do
+
+        let(:criteria) do
+          Band.where(name: "Nonexistent Band")
+        end
+
+        it "returns false" do
+          expect(criteria.any?).to be false
+        end
+      end
+    end
+
+    context "when called on class" do
+      context "with documents" do
+        before do
+          Band.create!(name: "New Band")
+        end
+
+        it "returns true" do
+          expect(Band.any?).to be true
+        end
+      end
+
+      context "with no documents" do
+        it "returns false" do
+          expect(Band.any?).to be false
+        end
+      end
+    end
+  end
+
+  describe "#one?" do
+    context "when called on criteria" do
+      let!(:band) do
+        Band.create!(name: "Depeche Mode")
+      end
+
+      let!(:band_two) do
+        Band.create!(name: "Radiohead")
+      end
+
+      context "when one document exists in criteria" do
+        let(:criteria) do
+          Band.where(name: "Depeche Mode")
+        end
+
+        it "returns true" do
+          expect(criteria.one?).to be true
+        end
+      end
+
+      context "when multiple documents exist in criteria" do
+        let(:criteria) do
+          Band.all
+        end
+
+        it "returns false" do
+          expect(criteria.one?).to be false
+        end
+      end
+
+      context "when no documents exist in criteria" do
+        let(:criteria) do
+          Band.where(name: "Nonexistent Band")
+        end
+
+        it "returns false" do
+          expect(criteria.one?).to be false
+        end
+      end
+    end
+
+    context "when called on class" do
+      context "with no documents" do
+        it "returns false" do
+          expect(Band.one?).to be false
+        end
+      end
+
+      context "with one document" do
+        before do
+          Band.create!(name: "Another Band")
+        end
+
+        it "returns true" do
+          expect(Band.one?).to be true
+        end
+      end
+
+      context "with multiple documents" do
+        before do
+          Band.create!(name: "New Band")
+          Band.create!(name: "Yet Another Band")
+        end
+
+        it "returns false" do
+          expect(Band.one?).to be false
+        end
+      end
+    end
+  end
+
+  describe "#many?" do
+    context "when called on criteria" do
+      let!(:band) do
+        Band.create!(name: "Depeche Mode")
+      end
+
+      let!(:band_two) do
+        Band.create!(name: "Radiohead")
+      end
+
+      context "when multiple documents exist in criteria" do
+        let(:criteria) do
+          Band.all
+        end
+
+        it "returns true" do
+          expect(criteria.many?).to be true
+        end
+      end
+
+      context "when one document exists in criteria" do
+        let(:criteria) do
+          Band.where(name: "Depeche Mode")
+        end
+
+        it "returns false" do
+          expect(criteria.many?).to be false
+        end
+      end
+
+      context "when no documents exist in criteria" do
+        let(:criteria) do
+          Band.where(name: "Nonexistent Band")
+        end
+
+        it "returns false" do
+          expect(criteria.many?).to be false
+        end
+      end
+
+    end
+
+    context "when called on class" do
+      context "with no documents" do
+        it "returns false" do
+          expect(Band.many?).to be false
+        end
+      end
+
+      context "with one document" do
+        before do
+          Band.create!(name: "Another Band")
+        end
+
+        it "returns false" do
+          expect(Band.many?).to be false
+        end
+      end
+
+      context "with multiple documents" do
+        before do
+          Band.create!(name: "New Band")
+          Band.create!(name: "Yet Another Band")
+        end
+
+        it "returns true" do
+          expect(Band.many?).to be true
+        end
+      end
+    end
+  end
+
   describe '#from_database_selector' do
     let(:criteria) { Mongoid::Criteria.new(Band) }
     let(:result) { criteria.send(:from_database_selector, [1]) }