1 files changed, 18 insertions, 1 deletions
diff --git a/objectivec/GPBExtensionRegistry.h b/objectivec/GPBExtensionRegistry.h
index ce1f8fab..e382971c 100644
--- a/objectivec/GPBExtensionRegistry.h
+++ b/objectivec/GPBExtensionRegistry.h
@@ -38,7 +38,24 @@
 // ExtensionRegistry in which you have registered any extensions that you want
 // to be able to parse.  Otherwise, those extensions will just be treated like
 // unknown fields.
-@interface GPBExtensionRegistry : NSObject
+//
+// The *Root classes provide +extensionRegistry for the extensions defined in a
+// given file *and* all files it imports.  You can also create a
+// GPBExtensionRegistry, and merge those registries to handle parsing extensions
+// defined from non overlapping files.
+//
+//    GPBExtensionRegistry *registry =
+//        [[[MyProtoFileRoot extensionRegistry] copy] autorelease];
+//    [registry addExtension:[OtherMessage neededExtension];  // Not in MyProtoFile
+//    NSError *parseError = nil;
+//    MyMessage *msg = [MyMessage parseData:data
+//                        extensionRegistry:registry
+//                                    error:&parseError];
+//
+@interface GPBExtensionRegistry : NSObject<NSCopying>
+
+- (void)addExtension:(GPBExtensionField *)extension;
+- (void)addExtensions:(GPBExtensionRegistry *)registry;
 
 - (GPBExtensionField *)getExtension:(GPBDescriptor *)containingType
                         fieldNumber:(NSInteger)fieldNumber;