Refactored module access to allow for lazy loading

Summary: public

The `bridge.modules` dictionary provides access to all native modules, but this API requires that every module is initialized in advance so that any module can be accessed.

This diff introduces a better API that will allow modules to be initialized lazily as they are needed, and deprecates `bridge.modules` (modules that use it will still work, but should be rewritten to use `bridge.moduleClasses` or `-[bridge moduleForName/Class:` instead.

The rules are now as follows:

* Any module that overrides `init` or `setBridge:` will be initialized on the main thread when the bridge is created
* Any module that implements `constantsToExport:` will be initialized later when the config is exported (the module itself will be initialized on a background queue, but  `constantsToExport:` will still be called on the main thread.
* All other modules will be initialized lazily when a method is first called on them.

These rules may seem slightly arcane, but they have the advantage of not violating any assumptions that may have been made by existing code - any module written under the original assumption that it would be initialized synchronously on the main thread when the bridge is created should still function exactly the same, but modules that avoid overriding `init` or `setBridge:` will now be loaded lazily.

I've rewritten most of the standard modules to take advantage of this new lazy loading, with the following results:

Out of the 65 modules included in UIExplorer:

* 16 are initialized on the main thread when the bridge is created
* A further 8 are initialized when the config is exported to JS
* The remaining 41 will be initialized lazily on-demand

Reviewed By: jspahrsummers

Differential Revision: D2677695

fb-gh-sync-id: 507ae7e9fd6b563e89292c7371767c978e928f33

Author: nicklockwood

Examples/UIExplorer/UIExplorer/NativeExampleViews/FlexibleSizeExampleView.m

@@ -52,8 +52,7 @@ @implementation FlexibleSizeExampleView
 
 - (instancetype)initWithFrame:(CGRect)frame
 {
-  self = [super initWithFrame:frame];
-  if (self) {
+  if ((self = [super initWithFrame:frame])) {
     _sizeUpdated = NO;
 
     AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];

Examples/UIExplorer/UIExplorerUnitTests/RCTEventDispatcherTests.m

@@ -62,7 +62,7 @@ - (void)setUp
 
   _bridge = [OCMockObject mockForClass:[RCTBridge class]];
   _eventDispatcher = [RCTEventDispatcher new];
-  ((id<RCTBridgeModule>)_eventDispatcher).bridge = _bridge;
+  [_eventDispatcher setValue:_bridge forKey:@"bridge"];
 
   _eventName = RCTNormalizeInputEventName(@"sampleEvent");
   _body = @{ @"foo": @"bar" };

Examples/UIExplorer/UIExplorerUnitTests/RCTGzipTests.m

@@ -16,6 +16,15 @@
 #import "RCTUtils.h"
 #import "RCTNetworking.h"
 
+#define RUN_RUNLOOP_WHILE(CONDITION) \
+_Pragma("clang diagnostic push") \
+_Pragma("clang diagnostic ignored \"-Wshadow\"") \
+NSDate *timeout = [[NSDate date] dateByAddingTimeInterval:5]; \
+while ((CONDITION) && [timeout timeIntervalSinceNow] > 0) { \
+  [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:timeout]; \
+} \
+_Pragma("clang diagnostic pop")
+
 extern BOOL RCTIsGzippedData(NSData *data);
 
 @interface RCTNetworking (Private)
@@ -61,18 +70,21 @@ - (void)testDontRezipZippedData
 - (void)testRequestBodyEncoding
 {
   NSDictionary *query = @{
-                          @"url": @"http://example.com",
-                          @"method": @"POST",
-                          @"data": @{@"string": @"Hello World"},
-                          @"headers": @{@"Content-Encoding": @"gzip"},
-                          };
+    @"url": @"http://example.com",
+    @"method": @"POST",
+    @"data": @{@"string": @"Hello World"},
+    @"headers": @{@"Content-Encoding": @"gzip"},
+  };
 
   RCTNetworking *networker = [RCTNetworking new];
+  [networker setValue:dispatch_get_main_queue() forKey:@"methodQueue"];
   __block NSURLRequest *request = nil;
   [networker buildRequest:query completionBlock:^(NSURLRequest *_request) {
     request = _request;
   }];
 
+  RUN_RUNLOOP_WHILE(request == nil);
+
   XCTAssertNotNil(request);
   XCTAssertNotNil(request.HTTPBody);
   XCTAssertTrue(RCTIsGzippedData(request.HTTPBody));

Libraries/CameraRoll/RCTAssetsLibraryImageLoader.m

@@ -151,7 +151,7 @@ @implementation RCTBridge (RCTAssetsLibraryImageLoader)
 
 - (ALAssetsLibrary *)assetsLibrary
 {
-  return [self.modules[RCTBridgeModuleNameForClass([RCTAssetsLibraryImageLoader class])] assetsLibrary];
+  return [[self moduleForClass:[RCTAssetsLibraryImageLoader class]] assetsLibrary];
 }
 
 @end

Libraries/CameraRoll/RCTImagePickerManager.m

@@ -32,16 +32,6 @@ @implementation RCTImagePickerManager
 
 RCT_EXPORT_MODULE(ImagePickerIOS);
 
-- (instancetype)init
-{
-  if ((self = [super init])) {
-    _pickers = [NSMutableArray new];
-    _pickerCallbacks = [NSMutableArray new];
-    _pickerCancelCallbacks = [NSMutableArray new];
-  }
-  return self;
-}
-
 - (dispatch_queue_t)methodQueue
 {
   return dispatch_get_main_queue();
@@ -67,8 +57,6 @@ - (dispatch_queue_t)methodQueue
     return;
   }
 
-  UIViewController *rootViewController = RCTKeyWindow().rootViewController;
-
   UIImagePickerController *imagePicker = [UIImagePickerController new];
   imagePicker.delegate = self;
   imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
@@ -77,11 +65,9 @@ - (dispatch_queue_t)methodQueue
     imagePicker.cameraCaptureMode = UIImagePickerControllerCameraCaptureModeVideo;
   }
 
-  [_pickers addObject:imagePicker];
-  [_pickerCallbacks addObject:callback];
-  [_pickerCancelCallbacks addObject:cancelCallback];
-
-  [rootViewController presentViewController:imagePicker animated:YES completion:nil];
+  [self _presentPicker:imagePicker
+       successCallback:callback
+        cancelCallback:cancelCallback];
 }
 
 RCT_EXPORT_METHOD(openSelectDialog:(NSDictionary *)config
@@ -93,8 +79,6 @@ - (dispatch_queue_t)methodQueue
     return;
   }
 
-  UIViewController *rootViewController = RCTKeyWindow().rootViewController;
-
   UIImagePickerController *imagePicker = [UIImagePickerController new];
   imagePicker.delegate = self;
   imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
@@ -109,30 +93,43 @@ - (dispatch_queue_t)methodQueue
 
   imagePicker.mediaTypes = allowedTypes;
 
-  [_pickers addObject:imagePicker];
-  [_pickerCallbacks addObject:callback];
-  [_pickerCancelCallbacks addObject:cancelCallback];
-
-  [rootViewController presentViewController:imagePicker animated:YES completion:nil];
+  [self _presentPicker:imagePicker
+       successCallback:callback
+        cancelCallback:cancelCallback];
 }
 
 - (void)imagePickerController:(UIImagePickerController *)picker
 didFinishPickingMediaWithInfo:(NSDictionary<NSString *, id> *)info
 {
-  NSUInteger index = [_pickers indexOfObject:picker];
-  RCTResponseSenderBlock callback = _pickerCallbacks[index];
+  [self _dismissPicker:picker args:@[
+    [info[UIImagePickerControllerReferenceURL] absoluteString]
+  ]];
+}
 
-  [_pickers removeObjectAtIndex:index];
-  [_pickerCallbacks removeObjectAtIndex:index];
-  [_pickerCancelCallbacks removeObjectAtIndex:index];
+- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
+{
+  [self _dismissPicker:picker args:nil];
+}
 
-  UIViewController *rootViewController = RCTKeyWindow().rootViewController;
-  [rootViewController dismissViewControllerAnimated:YES completion:nil];
+- (void)_presentPicker:(UIImagePickerController *)imagePicker
+       successCallback:(RCTResponseSenderBlock)callback
+        cancelCallback:(RCTResponseSenderBlock)cancelCallback
+{
+  if (!_pickers) {
+    _pickers = [NSMutableArray new];
+    _pickerCallbacks = [NSMutableArray new];
+    _pickerCancelCallbacks = [NSMutableArray new];
+  }
+
+  [_pickers addObject:imagePicker];
+  [_pickerCallbacks addObject:callback];
+  [_pickerCancelCallbacks addObject:cancelCallback];
 
-  callback(@[[info[UIImagePickerControllerReferenceURL] absoluteString]]);
+  UIViewController *rootViewController = RCTKeyWindow().rootViewController;
+  [rootViewController presentViewController:imagePicker animated:YES completion:nil];
 }
 
-- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
+- (void)_dismissPicker:(UIImagePickerController *)picker args:(NSArray *)args
 {
   NSUInteger index = [_pickers indexOfObject:picker];
   RCTResponseSenderBlock callback = _pickerCancelCallbacks[index];
@@ -144,7 +141,7 @@ - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
   UIViewController *rootViewController = RCTKeyWindow().rootViewController;
   [rootViewController dismissViewControllerAnimated:YES completion:nil];
 
-  callback(@[]);
+  callback(args ?: @[]);
 }
 
 @end

Libraries/Geolocation/RCTLocationObserver.m

@@ -111,19 +111,6 @@ @implementation RCTLocationObserver
 
 #pragma mark - Lifecycle
 
-- (instancetype)init
-{
-  if ((self = [super init])) {
-
-    _locationManager = [CLLocationManager new];
-    _locationManager.distanceFilter = RCT_DEFAULT_LOCATION_ACCURACY;
-    _locationManager.delegate = self;
-
-    _pendingRequests = [NSMutableArray new];
-  }
-  return self;
-}
-
 - (void)dealloc
 {
   [_locationManager stopUpdatingLocation];
@@ -139,6 +126,13 @@ - (dispatch_queue_t)methodQueue
 
 - (void)beginLocationUpdates
 {
+  if (!_locationManager) {
+    _locationManager = [CLLocationManager new];
+    _locationManager.distanceFilter = RCT_DEFAULT_LOCATION_ACCURACY;
+    _locationManager.delegate = self;
+    _pendingRequests = [NSMutableArray new];
+  }
+
   // Request location access permission
   if ([_locationManager respondsToSelector:@selector(requestWhenInUseAuthorization)]) {
     [_locationManager requestWhenInUseAuthorization];

Libraries/Image/RCTImageLoader.m

@@ -45,17 +45,17 @@ @implementation RCTImageLoader
 
 RCT_EXPORT_MODULE()
 
-- (void)setBridge:(RCTBridge *)bridge
+- (void)setUp
 {
   // Get image loaders and decoders
   NSMutableArray<id<RCTImageURLLoader>> *loaders = [NSMutableArray array];
   NSMutableArray<id<RCTImageDataDecoder>> *decoders = [NSMutableArray array];
-  for (id<RCTBridgeModule> module in bridge.modules.allValues) {
-    if ([module conformsToProtocol:@protocol(RCTImageURLLoader)]) {
-      [loaders addObject:(id<RCTImageURLLoader>)module];
+  for (Class moduleClass in _bridge.moduleClasses) {
+    if ([moduleClass conformsToProtocol:@protocol(RCTImageURLLoader)]) {
+      [loaders addObject:[_bridge moduleForClass:moduleClass]];
     }
-    if ([module conformsToProtocol:@protocol(RCTImageDataDecoder)]) {
-      [decoders addObject:(id<RCTImageDataDecoder>)module];
+    if ([moduleClass conformsToProtocol:@protocol(RCTImageDataDecoder)]) {
+      [decoders addObject:[_bridge moduleForClass:moduleClass]];
     }
   }
 
@@ -85,17 +85,16 @@ - (void)setBridge:(RCTBridge *)bridge
     }
   }];
 
-  _bridge = bridge;
   _loaders = loaders;
   _decoders = decoders;
-  _URLCacheQueue = dispatch_queue_create("com.facebook.react.ImageLoaderURLCacheQueue", DISPATCH_QUEUE_SERIAL);
-  _URLCache = [[NSURLCache alloc] initWithMemoryCapacity:5 * 1024 * 1024 // 5MB
-                                            diskCapacity:200 * 1024 * 1024 // 200MB
-                                                diskPath:@"React/RCTImageDownloader"];
 }
 
 - (id<RCTImageURLLoader>)imageURLLoaderForURL:(NSURL *)URL
 {
+  if (!_loaders) {
+    [self setUp];
+  }
+
   if (RCT_DEBUG) {
     // Check for handler conflicts
     float previousPriority = 0;
@@ -133,6 +132,10 @@ - (void)setBridge:(RCTBridge *)bridge
 
 - (id<RCTImageDataDecoder>)imageDataDecoderForData:(NSData *)data
 {
+  if (!_decoders) {
+    [self setUp];
+  }
+
   if (RCT_DEBUG) {
     // Check for handler conflicts
     float previousPriority = 0;
@@ -212,7 +215,17 @@ - (RCTImageLoaderCancellationBlock)loadImageWithTag:(NSString *)imageTag
   }
 
   // All access to URL cache must be serialized
+  if (!_URLCacheQueue) {
+    _URLCacheQueue = dispatch_queue_create("com.facebook.react.ImageLoaderURLCacheQueue", DISPATCH_QUEUE_SERIAL);
+  }
   dispatch_async(_URLCacheQueue, ^{
+
+    if (!_URLCache) {
+      _URLCache = [[NSURLCache alloc] initWithMemoryCapacity:5 * 1024 * 1024 // 5MB
+                                                diskCapacity:200 * 1024 * 1024 // 200MB
+                                                    diskPath:@"React/RCTImageDownloader"];
+    }
+
     RCTImageLoader *strongSelf = weakSelf;
     if (cancelled || !strongSelf) {
       return;
@@ -385,14 +398,7 @@ - (RCTImageLoaderCancellationBlock)decodeImageData:(NSData *)data
 
 - (BOOL)canHandleRequest:(NSURLRequest *)request
 {
-  NSURL *requestURL = request.URL;
-  for (id<RCTBridgeModule> module in _bridge.modules.allValues) {
-    if ([module conformsToProtocol:@protocol(RCTImageURLLoader)] &&
-        [(id<RCTImageURLLoader>)module canLoadImageURL:requestURL]) {
-      return YES;
-    }
-  }
-  return NO;
+  return [self imageURLLoaderForURL:request.URL] != nil;
 }
 
 - (id)sendRequest:(NSURLRequest *)request withDelegate:(id<RCTURLRequestDelegate>)delegate
@@ -440,7 +446,7 @@ @implementation RCTBridge (RCTImageLoader)
 
 - (RCTImageLoader *)imageLoader
 {
-  return self.modules[RCTBridgeModuleNameForClass([RCTImageLoader class])];
+  return [self moduleForClass:[RCTImageLoader class]];
 }
 
 @end

Libraries/Image/RCTImageStoreManager.m

@@ -30,15 +30,6 @@ @implementation RCTImageStoreManager
 
 RCT_EXPORT_MODULE()
 
-- (instancetype)init
-{
-  if ((self = [super init])) {
-    _store = [NSMutableDictionary new];
-    _id = 0;
-  }
-  return self;
-}
-
 - (void)removeImageForTag:(NSString *)imageTag withBlock:(void (^)())block
 {
   dispatch_async(_methodQueue, ^{
@@ -52,6 +43,12 @@ - (void)removeImageForTag:(NSString *)imageTag withBlock:(void (^)())block
 - (NSString *)_storeImageData:(NSData *)imageData
 {
   RCTAssertThread(_methodQueue, @"Must be called on RCTImageStoreManager thread");
+
+  if (!_store) {
+    _store = [NSMutableDictionary new];
+    _id = 0;
+  }
+
   NSString *imageTag = [NSString stringWithFormat:@"%@://%tu", RCTImageStoreURLScheme, _id++];
   _store[imageTag] = imageData;
   return imageTag;
@@ -225,7 +222,7 @@ @implementation RCTBridge (RCTImageStoreManager)
 
 - (RCTImageStoreManager *)imageStoreManager
 {
-  return self.modules[RCTBridgeModuleNameForClass([RCTImageStoreManager class])];
+  return [self moduleForClass:[RCTImageStoreManager class]];
 }
 
 @end

Libraries/LinkingIOS/RCTLinkingManager.m

@@ -21,15 +21,20 @@ @implementation RCTLinkingManager
 
 RCT_EXPORT_MODULE()
 
-- (instancetype)init
+- (void)setBridge:(RCTBridge *)bridge
 {
-  if ((self = [super init])) {
-    [[NSNotificationCenter defaultCenter] addObserver:self
-                                             selector:@selector(handleOpenURLNotification:)
-                                                 name:RCTOpenURLNotification
-                                               object:nil];
-  }
-  return self;
+  _bridge = bridge;
+
+  [[NSNotificationCenter defaultCenter] addObserver:self
+                                           selector:@selector(handleOpenURLNotification:)
+                                               name:RCTOpenURLNotification
+                                             object:nil];
+}
+
+- (NSDictionary<NSString *, id> *)constantsToExport
+{
+  NSURL *initialURL = _bridge.launchOptions[UIApplicationLaunchOptionsURLKey];
+  return @{@"initialURL": RCTNullIfNil(initialURL.absoluteString)};
 }
 
 - (void)dealloc
@@ -75,10 +80,4 @@ - (void)handleOpenURLNotification:(NSNotification *)notification
   callback(@[@(canOpen)]);
 }
 
-- (NSDictionary<NSString *, id> *)constantsToExport
-{
-  NSURL *initialURL = _bridge.launchOptions[UIApplicationLaunchOptionsURLKey];
-  return @{@"initialURL": RCTNullIfNil(initialURL.absoluteString)};
-}
-
 @end