Allow nullable field (#40)

src/Enum.php

@@ -36,7 +36,14 @@ function (NovaRequest $request, $model, $attribute, $requestAttribute) {
     public function attach($class)
     {
         return $this->options($class::asSelectArray())
-                    ->rules('required', new EnumValue($class, false));
+                    ->rules($this->nullable ? 'nullable' : 'required', new EnumValue($class, false));
+    }
+
+    public function nullable($nullable = true, $values = null)
+    {
+        $this->rules = str_replace('required', 'nullable', $this->rules);
+
+        return parent::nullable($nullable, $values);
     }
 
     /**

src/FlaggedEnum.php

@@ -8,12 +8,7 @@
 
 class FlaggedEnum extends BooleanGroup
 {
-    public function __construct($name, $attribute = null, $resolveCallback = null)
-    {
-        parent::__construct($name, $attribute, $resolveCallback);
-
-        $this->noValueText('None');
-    }
+    public $noValueText = 'None';
 
     public function attach($class)
     {

tests/Fields/FieldTest.php

@@ -3,6 +3,7 @@
 namespace SimpleSquid\Nova\Fields\Enum\Tests\Fields;
 
 use BenSampo\Enum\Rules\EnumValue;
+use Laravel\Nova\Http\Requests\NovaRequest;
 use SimpleSquid\Nova\Fields\Enum\Enum;
 use SimpleSquid\Nova\Fields\Enum\Tests\Examples\IntegerEnum;
 use SimpleSquid\Nova\Fields\Enum\Tests\TestCase;
@@ -56,4 +57,14 @@ public function it_displays_enum_options()
                                   ], $this->field->meta['options']);
         }
     }
+
+    /** @test */
+    public function it_can_be_nullable()
+    {
+        $this->field->nullable();
+
+        $this->assertNotContains('required', $this->field->rules);
+        $this->assertContains('nullable', $this->field->rules);
+        $this->assertFalse($this->field->isRequired(new NovaRequest()));
+    }
 }