Fabric: Default implementation of RCTComponentViewProtocol

Summary:
All methods of RCTComponentViewProtocol are non-optional,
but this default implementation removes necessity to implement all of them manually.

Reviewed By: mdvacca

Differential Revision: D7507522

fbshipit-source-id: e4dff97e8bf64e79d2f1ffca94f0549bd4b5e2fa

React/Fabric/Mounting/UIView+ComponentViewProtocol.h

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import <UIKit/UIKit.h>
+
+#import <React/RCTComponentViewProtocol.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * Default implementation of RCTComponentViewProtocol.
+ */
+@interface UIView (ComponentViewProtocol)
+
+- (void)mountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView
+                          index:(NSInteger)index;
+
+- (void)unmountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView
+                            index:(NSInteger)index;
+
+- (void)updateProps:(facebook::react::SharedProps)props
+           oldProps:(facebook::react::SharedProps)oldProps;
+
+- (void)updateLayoutMetrics:(facebook::react::LayoutMetrics)layoutMetrics
+           oldLayoutMetrics:(facebook::react::LayoutMetrics)oldLayoutMetrics;
+
+- (void)prepareForRecycle;
+
+@end
+
+NS_ASSUME_NONNULL_END

React/Fabric/Mounting/UIView+ComponentViewProtocol.mm

@@ -0,0 +1,57 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import "UIView+ComponentViewProtocol.h"
+
+#import <React/RCTAssert.h>
+
+@implementation UIView (ComponentViewProtocol)
+
+- (void)mountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView
+                          index:(NSInteger)index
+{
+  [self insertSubview:childComponentView atIndex:index];
+}
+
+- (void)unmountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView
+                            index:(NSInteger)index
+{
+  RCTAssert(childComponentView.superview == self, @"Attempt to unmount improperly mounted component view.");
+  [childComponentView removeFromSuperview];
+}
+
+- (void)updateProps:(facebook::react::SharedProps)props
+           oldProps:(facebook::react::SharedProps)oldProps
+{
+  // Default implementation does nothing.
+}
+
+- (void)updateLayoutMetrics:(facebook::react::LayoutMetrics)layoutMetrics
+           oldLayoutMetrics:(facebook::react::LayoutMetrics)oldLayoutMetrics
+{
+  if (layoutMetrics.frame != oldLayoutMetrics.frame) {
+    self.frame = {
+      .origin = {
+        .x = layoutMetrics.frame.origin.x,
+        .y = layoutMetrics.frame.origin.y
+      },
+      .size = {
+        .width = layoutMetrics.frame.size.width,
+        .height = layoutMetrics.frame.size.height
+      }
+    };
+  }
+
+  // TODO: Apply another layout metrics here.
+}
+
+- (void)prepareForRecycle
+{
+  // Default implementation does nothing.
+}
+
+@end