Add class/2 for conditional checking

lib/ex_css_modules/ex_css_modules.ex

@@ -43,11 +43,28 @@ defmodule ExCSSModules do
   def class(definition, classes) do
     definition
     |> class_name(classes)
-    |> class_attribute
+    |> class_attribute()
   end
 
   @doc """
-  Returns the class name from the definition map is value is true.
+  If `value` is truthy, read the class definitions and maps them to a class attribute.
+  When `value` is falsy return nil.
+
+  ## Examples
+    iex> class(%{ "hello" => "world"}, "hello", true)
+    {:safe, ~s(class="world")}
+
+    iex> class(%{ "hello" => "world"}, "hello", false)
+    nil
+  """
+  def class(definition, classes, value) do
+    definition
+    |> class_name(classes, value)
+    |> class_attribute()
+  end
+
+  @doc """
+  Returns the class name from the definition map if value is true.
 
   ## Examples
     iex> class_name(%{"hello" => "world"}, "hello", true)
@@ -63,7 +80,7 @@ defmodule ExCSSModules do
   end
 
   @doc """
-  Returns the class name from the definition map is the second argument
+  Returns the class name from the definition map if the second argument
   in the tuple is true.
 
   ## Examples
@@ -89,12 +106,15 @@ defmodule ExCSSModules do
 
     iex> class_name(%{"hello" => "world", "foo" => "bar"}, [{"hello", true}, {"foo", false}])
     "world"
+
+    iex> class_name(%{"hello" => "world", "foo" => "bar"}, [{"hello", false}])
+    nil
   """
   def class_name(definition, keys) when is_list(keys) do
     keys
     |> Enum.map(&class_name(definition, &1))
     |> Enum.reject(&is_nil/1)
-    |> Enum.join(" ")
+    |> join_class_name()
   end
 
   @doc """
@@ -139,5 +159,9 @@ defmodule ExCSSModules do
     end
   end
 
+  defp class_attribute(nil), do: nil
   defp class_attribute(class), do: HTML.raw(~s(class="#{class}"))
+
+  defp join_class_name(list) when length(list) == 0, do: nil
+  defp join_class_name(list), do: Enum.join(list, " ")
 end

lib/ex_css_modules/view.ex

@@ -40,6 +40,7 @@ defmodule ExCSSModules.View do
       def stylesheet, do: ExCSSModules.stylesheet(@stylesheet)
 
       def class(key), do: stylesheet() |> ExCSSModules.class(key)
+      def class(key, value), do: stylesheet() |> ExCSSModules.class(key, value)
 
       def class_name(key) do
         ExCSSModules.class_name(stylesheet(), key)

test/ex_css_modules/ex_css_modules_test.exs

@@ -19,6 +19,33 @@ defmodule ExCSSModulesTest do
     end
   end
 
+  describe "class/2" do
+    test "returns a class attribute for an existing classname" do
+      assert ExCSSModules.class(
+        %{"hello" => "world"},
+        "hello"
+      ) == {:safe, ~s(class="world")}
+    end
+
+    test "returns nil for a non existing classname" do
+      assert ExCSSModules.class(%{"hello" => "world"}, "foo") == nil
+    end
+  end
+
+  describe "class/3" do
+    test "returns a class attribute for an existing classname when value is true" do
+      assert ExCSSModules.class(
+        %{"hello" => "world"},
+        "hello",
+        true
+      ) == {:safe, ~s(class="world")}
+    end
+
+    test "returns nil for an existing classname when value is false" do
+      assert ExCSSModules.class(%{"hello" => "world"}, "hello", false) == nil
+    end
+  end
+
   describe "class_name/3" do
     test "returns the definition when value is true" do
       assert ExCSSModules.class_name(
@@ -63,6 +90,13 @@ defmodule ExCSSModulesTest do
       ) == "world"
     end
 
+    test "returns nil for an existing classname when value is false" do
+      assert ExCSSModules.class_name(
+        %{"hello" => "world", "foo" => "bar"},
+        [{"hello", false}]
+      ) == nil
+    end
+
     test "defaults to nil" do
       assert ExCSSModules.class_name(%{}, "hello") == nil
     end

test/ex_css_modules/view_test.exs

@@ -61,9 +61,18 @@ defmodule ExCSSModules.ViewTest do
   end
 
   describe "class/1" do
-    test "creates a safe Phoenix HTML class based on the stylesheet" do
+    test "calls the class/2 method on ExCSSModules" do
       assert ViewModuleTest.class("title") ==
         ExCSSModules.class(@example_stylesheet, "title")
     end
   end
+
+  describe "class/2" do
+    test "calls the class/3 method on ExCSSModules" do
+      assert ViewModuleTest.class("title", true) ==
+        ExCSSModules.class(@example_stylesheet, "title", true)
+      assert ViewModuleTest.class("title", false) ==
+        ExCSSModules.class(@example_stylesheet, "title", false)
+    end
+  end
 end