Lay groundwork for Fabric iOS plugins

Summary: Changelog: [Internal]

Reviewed By: fkgozali

Differential Revision: D18397243

fbshipit-source-id: bae51800e93259e50db51dac2d9d7b4b52d8ef23

React/Fabric/Mounting/RCTComponentViewFactory.h

@@ -14,6 +14,16 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+@protocol RCTComponentViewFactoryDelegate <NSObject>
+
+/**
+ * Given a component name, return its actual class. If component with doesn't exist, nil is returned.
+ * Can be called on any thread.
+ */
+- (Class<RCTComponentViewProtocol>)componentViewClassWithName:(facebook::react::ComponentName)name;
+
+@end
+
 /**
  * Registry of supported component view classes that can instantiate
  * view component instances by given component handle.
@@ -42,6 +52,8 @@ NS_ASSUME_NONNULL_BEGIN
 - (facebook::react::ComponentDescriptorRegistry::Shared)createComponentDescriptorRegistryWithParameters:
     (facebook::react::ComponentDescriptorParameters)parameters;
 
+@property (atomic, weak, nullable) id<RCTComponentViewFactoryDelegate> delegate;
+
 @end
 
 NS_ASSUME_NONNULL_END

React/Fabric/Mounting/RCTComponentViewFactory.mm

@@ -66,8 +66,15 @@ using namespace facebook::react;
 
   providerRegistry->setComponentDescriptorProviderRequest([providerRegistry,
                                                            componentViewFactory](ComponentName requestedComponentName) {
-    // Fallback 1: Call the delegate.
-    // To be implemented.
+    // Fallback 1: Call delegate for component view class.
+    if (componentViewFactory.delegate) {
+      Class<RCTComponentViewProtocol> klass =
+          [componentViewFactory.delegate componentViewClassWithName:requestedComponentName];
+      if (klass) {
+        [componentViewFactory registerComponentViewClass:klass];
+        return;
+      }
+    }
 
     // Fallback 2: Try to use Paper Interop.
     if ([RCTLegacyViewManagerInteropComponentView isSupported:RCTNSStringFromString(requestedComponentName)]) {

React/Fabric/RCTSurfacePresenter.h

@@ -10,6 +10,7 @@
 #import <React/RCTPrimitives.h>
 #import <React/RCTSurfacePresenterStub.h>
 
+#import <React/RCTComponentViewFactory.h>
 #import <react/utils/ContextContainer.h>
 #import <react/utils/RuntimeExecutor.h>
 
@@ -18,7 +19,6 @@ NS_ASSUME_NONNULL_BEGIN
 @class RCTFabricSurface;
 @class RCTImageLoader;
 @class RCTMountingManager;
-@class RCTComponentViewFactory;
 
 /**
  * Coordinates presenting of React Native Surfaces and represents application