fix #2230

Author: soyuka

core/content-negotiation.md

@@ -309,6 +309,14 @@ final class CustomItemNormalizer implements NormalizerInterface, DenormalizerInt
     {
         return $this->normalizer->supportsNormalization($data, $format);
     }
+
+    public function getSupportedTypes(?string $format): array
+    {
+        return [
+            'object' => null,
+            '*' => false,
+        ];
+    }
 }
 ```
 
@@ -348,6 +356,8 @@ class CustomItemNormalizer implements NormalizerInterface, DenormalizerInterface
 }
 ```
 
+Read more about the [serialization here](./serialization) or check out how to decode [Form Data](./form-data)
+
 ### Contributing Support for New Formats
 
 Adding support for **standard** formats upstream is welcome! We'll be glad to

core/serialization.md

@@ -1042,6 +1042,13 @@ class BookAttributeNormalizer implements NormalizerInterface, NormalizerAwareInt
         // for the current $object (book) and
         // return true or false
     }
+
+    public function getSupportedTypes(?string $format): array
+    {
+        return [
+            Book::class => true
+        ];
+    }
 }
 ```
 
@@ -1149,6 +1156,11 @@ final class ApiNormalizer implements NormalizerInterface, DenormalizerInterface,
             $this->decorated->setSerializer($serializer);
         }
     }
+
+    public function getSupportedTypes(?string $format): array
+    {
+        return $this->decorated->getSupportedTypes($format);
+    }
 }
 ```