Refactor reload command in React Native

Summary: Introduces an API to register a weakly-held listener for the reload (Cmd+R) command. This allows external infrastructure to hook into the reload command before the `RCTBridge` object is even created.

Reviewed By: javache

Differential Revision: D4286980

fbshipit-source-id: 51012fb8cbeb433dc880d9d98d847b07fdbb4c4f

React/Base/RCTBridge.m

@@ -14,11 +14,11 @@
 
 #import "RCTConvert.h"
 #import "RCTEventDispatcher.h"
-#import "RCTKeyCommands.h"
 #import "RCTLog.h"
 #import "RCTModuleData.h"
 #import "RCTPerformanceLogger.h"
 #import "RCTProfile.h"
+#import "RCTReloadCommand.h"
 #import "RCTUtils.h"
 
 NSString *const RCTJavaScriptWillStartLoadingNotification = @"RCTJavaScriptWillStartLoadingNotification";
@@ -119,6 +119,9 @@ void RCTVerifyAllModulesExported(NSArray *extraModules)
 }
 #endif
 
+@interface RCTBridge () <RCTReloadListener>
+@end
+
 @implementation RCTBridge
 {
   NSURL *_delegateBundleURL;
@@ -207,18 +210,15 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   RCTAssertMainQueue();
 
 #if TARGET_IPHONE_SIMULATOR
-  RCTKeyCommands *commands = [RCTKeyCommands sharedInstance];
-
-  // reload in current mode
-  __weak typeof(self) weakSelf = self;
-  [commands registerKeyCommandWithInput:@"r"
-                          modifierFlags:UIKeyModifierCommand
-                                 action:^(__unused UIKeyCommand *command) {
-    [weakSelf reload];
-  }];
+  RCTRegisterReloadCommandListener(self);
 #endif
 }
 
+- (void)didReceiveReloadCommand
+{
+  [self reload];
+}
+
 - (NSArray<Class> *)moduleClasses
 {
   return self.batchedBridge.moduleClasses;

React/Base/RCTReloadCommand.h

@@ -0,0 +1,19 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import <React/RCTDefines.h>
+
+@protocol RCTReloadListener
+- (void)didReceiveReloadCommand;
+@end
+
+/** Registers a weakly-held observer of the Command+R reload key command. */
+RCT_EXTERN void RCTRegisterReloadCommandListener(id<RCTReloadListener> listener);

React/Base/RCTReloadCommand.m

@@ -0,0 +1,37 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "RCTReloadCommand.h"
+
+#import "RCTKeyCommands.h"
+
+void RCTRegisterReloadCommandListener(id<RCTReloadListener> listener)
+{
+  static NSHashTable<id<RCTReloadListener>> *listeners;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    listeners = [NSHashTable weakObjectsHashTable];
+    [[RCTKeyCommands sharedInstance] registerKeyCommandWithInput:@"r"
+                                                   modifierFlags:UIKeyModifierCommand
+                                                          action:
+     ^(__unused UIKeyCommand *command) {
+       NSArray<id<RCTReloadListener>> *copiedListeners;
+       @synchronized (listeners) { // avoid mutation-while-enumerating
+         copiedListeners = [listeners allObjects];
+       }
+       for (id<RCTReloadListener> l in copiedListeners) {
+         [l didReceiveReloadCommand];
+       }
+     }];
+  });
+
+  @synchronized (listeners) {
+    [listeners addObject:listener];
+  }
+}