react-native/React/Base/RCTModuleData.mm

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

#import "RCTModuleData.h"

#import <objc/runtime.h>
#include <mutex>

#import "RCTBridge+Private.h"
#import "RCTBridge.h"
#import "RCTLog.h"
#import "RCTModuleMethod.h"
#import "RCTProfile.h"
#import "RCTUtils.h"

@implementation RCTModuleData
{
  NSDictionary<NSString *, id> *_constantsToExport;
  NSString *_queueName;
  __weak RCTBridge *_bridge;
  RCTBridgeModuleProvider _moduleProvider;
  std::mutex _instanceLock;
  BOOL _setupComplete;
}

@synthesize methods = _methods;
@synthesize instance = _instance;
@synthesize methodQueue = _methodQueue;

- (void)setUp
{
  _implementsBatchDidComplete = [_moduleClass instancesRespondToSelector:@selector(batchDidComplete)];
  _implementsPartialBatchDidFlush = [_moduleClass instancesRespondToSelector:@selector(partialBatchDidFlush)];

  // If a module overrides `constantsToExport` and doesn't implement `requiresMainQueueSetup`, then we must assume
  // that it must be called on the main thread, because it may need to access UIKit.
  _hasConstantsToExport = [_moduleClass instancesRespondToSelector:@selector(constantsToExport)];

  const BOOL implementsRequireMainQueueSetup = [_moduleClass respondsToSelector:@selector(requiresMainQueueSetup)];
  if (implementsRequireMainQueueSetup) {
    _requiresMainQueueSetup = [_moduleClass requiresMainQueueSetup];
  } else {
    static IMP objectInitMethod;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
      objectInitMethod = [NSObject instanceMethodForSelector:@selector(init)];
    });

    // If a module overrides `init` then we must assume that it expects to be
    // initialized on the main thread, because it may need to access UIKit.
    const BOOL hasCustomInit = !_instance && [_moduleClass instanceMethodForSelector:@selector(init)] != objectInitMethod;

    _requiresMainQueueSetup = _hasConstantsToExport || hasCustomInit;
    if (_requiresMainQueueSetup) {
      const char *methodName = "";
      if (_hasConstantsToExport) {
        methodName = "constantsToExport";
      } else if (hasCustomInit) {
        methodName = "init";
      }
      RCTLogWarn(@"Module %@ requires main queue setup since it overrides `%s` but doesn't implement "
        "`requiresMainQueueSetup`. In a future release React Native will default to initializing all native modules "
        "on a background thread unless explicitly opted-out of.", _moduleClass, methodName);
    }
  }
}

- (instancetype)initWithModuleClass:(Class)moduleClass
                             bridge:(RCTBridge *)bridge
{
  return [self initWithModuleClass:moduleClass
                    moduleProvider:^id<RCTBridgeModule>{ return [moduleClass new]; }
                            bridge:bridge];
}

- (instancetype)initWithModuleClass:(Class)moduleClass
                     moduleProvider:(RCTBridgeModuleProvider)moduleProvider
                             bridge:(RCTBridge *)bridge
{
  if (self = [super init]) {
    _bridge = bridge;
    _moduleClass = moduleClass;
    _moduleProvider = [moduleProvider copy];
    [self setUp];
  }
  return self;
}

- (instancetype)initWithModuleInstance:(id<RCTBridgeModule>)instance
                                bridge:(RCTBridge *)bridge
{
  if (self = [super init]) {
    _bridge = bridge;
    _instance = instance;
    _moduleClass = [instance class];
    [self setUp];
  }
  return self;
}

RCT_NOT_IMPLEMENTED(- (instancetype)init);

#pragma mark - private setup methods

- (void)setUpInstanceAndBridge
{
  RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, @"[RCTModuleData setUpInstanceAndBridge]", @{
    @"moduleClass": NSStringFromClass(_moduleClass)
  });
  {
    std::unique_lock<std::mutex> lock(_instanceLock);

    if (!_setupComplete && _bridge.valid) {
      if (!_instance) {
        if (RCT_DEBUG && _requiresMainQueueSetup) {
          RCTAssertMainQueue();
        }
        RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, @"[RCTModuleData setUpInstanceAndBridge] Create module", nil);
        _instance = _moduleProvider ? _moduleProvider() : nil;
        RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
        if (!_instance) {
          // Module init returned nil, probably because automatic instantatiation
          // of the module is not supported, and it is supposed to be passed in to
          // the bridge constructor. Mark setup complete to avoid doing more work.
          _setupComplete = YES;
          RCTLogWarn(@"The module %@ is returning nil from its constructor. You "
                     "may need to instantiate it yourself and pass it into the "
                     "bridge.", _moduleClass);
        }
      }

      if (_instance && RCTProfileIsProfiling()) {
        RCTProfileHookInstance(_instance);
      }

      // Bridge must be set before methodQueue is set up, as methodQueue
      // initialization requires it (View Managers get their queue by calling
      // self.bridge.uiManager.methodQueue)
      [self setBridgeForInstance];
    }

    [self setUpMethodQueue];
  }
  RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");

  // This is called outside of the lock in order to prevent deadlock issues
  // because the logic in `finishSetupForInstance` can cause
  // `moduleData.instance` to be accessed re-entrantly.
  if (_bridge.moduleSetupComplete) {
    [self finishSetupForInstance];
  } else {
    // If we're here, then the module is completely initialized,
    // except for what finishSetupForInstance does.  When the instance
    // method is called after moduleSetupComplete,
    // finishSetupForInstance will run.  If _requiresMainQueueSetup
    // is true, getting the instance will block waiting for the main
    // thread, which could take a while if the main thread is busy
    // (I've seen 50ms in testing).  So we clear that flag, since
    // nothing in finishSetupForInstance needs to be run on the main
    // thread.
    _requiresMainQueueSetup = NO;
  }
}

- (void)setBridgeForInstance
{
  if ([_instance respondsToSelector:@selector(bridge)] && _instance.bridge != _bridge) {
    RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, @"[RCTModuleData setBridgeForInstance]", nil);
    @try {
      [(id)_instance setValue:_bridge forKey:@"bridge"];
    }
    @catch (NSException *exception) {
      RCTLogError(@"%@ has no setter or ivar for its bridge, which is not "
                  "permitted. You must either @synthesize the bridge property, "
                  "or provide your own setter method.", self.name);
    }
    RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
  }
}

- (void)finishSetupForInstance
{
  if (!_setupComplete && _instance) {
    RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, @"[RCTModuleData finishSetupForInstance]", nil);
    _setupComplete = YES;
    [_bridge registerModuleForFrameUpdates:_instance withModuleData:self];
    [[NSNotificationCenter defaultCenter] postNotificationName:RCTDidInitializeModuleNotification
                                                        object:_bridge
                                                      userInfo:@{@"module": _instance, @"bridge": RCTNullIfNil(_bridge.parentBridge)}];
    RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
  }
}

- (void)setUpMethodQueue
{
  if (_instance && !_methodQueue && _bridge.valid) {
    RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, @"[RCTModuleData setUpMethodQueue]", nil);
    BOOL implementsMethodQueue = [_instance respondsToSelector:@selector(methodQueue)];
    if (implementsMethodQueue && _bridge.valid) {
      _methodQueue = _instance.methodQueue;
    }
    if (!_methodQueue && _bridge.valid) {
      // Create new queue (store queueName, as it isn't retained by dispatch_queue)
      _queueName = [NSString stringWithFormat:@"com.facebook.react.%@Queue", self.name];
      _methodQueue = dispatch_queue_create(_queueName.UTF8String, DISPATCH_QUEUE_SERIAL);

      // assign it to the module
      if (implementsMethodQueue) {
        @try {
          [(id)_instance setValue:_methodQueue forKey:@"methodQueue"];
        }
        @catch (NSException *exception) {
          RCTLogError(@"%@ is returning nil for its methodQueue, which is not "
                      "permitted. You must either return a pre-initialized "
                      "queue, or @synthesize the methodQueue to let the bridge "
                      "create a queue for you.", self.name);
        }
      }
    }
    RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
  }
}

#pragma mark - public getters

- (BOOL)hasInstance
{
  std::unique_lock<std::mutex> lock(_instanceLock);
  return _instance != nil;
}

- (id<RCTBridgeModule>)instance
{
  if (!_setupComplete) {
    RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, ([NSString stringWithFormat:@"[RCTModuleData instanceForClass:%@]", _moduleClass]), nil);
    if (_requiresMainQueueSetup) {
      // The chances of deadlock here are low, because module init very rarely
      // calls out to other threads, however we can't control when a module might
      // get accessed by client code during bridge setup, and a very low risk of
      // deadlock is better than a fairly high risk of an assertion being thrown.
      RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, @"[RCTModuleData instance] main thread setup", nil);

      if (!RCTIsMainQueue()) {
        RCTLogWarn(@"RCTBridge required dispatch_sync to load %@. This may lead to deadlocks", _moduleClass);
      }

      RCTUnsafeExecuteOnMainQueueSync(^{
        [self setUpInstanceAndBridge];
      });
      RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
    } else {
      [self setUpInstanceAndBridge];
    }
    RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
  }
  return _instance;
}

- (NSString *)name
{
  return RCTBridgeModuleNameForClass(_moduleClass);
}

- (NSArray<id<RCTBridgeMethod>> *)methods
{
  if (!_methods) {
    NSMutableArray<id<RCTBridgeMethod>> *moduleMethods = [NSMutableArray new];

    if ([_moduleClass instancesRespondToSelector:@selector(methodsToExport)]) {
      [moduleMethods addObjectsFromArray:[self.instance methodsToExport]];
    }

    unsigned int methodCount;
    Class cls = _moduleClass;
    while (cls && cls != [NSObject class] && cls != [NSProxy class]) {
      Method *methods = class_copyMethodList(object_getClass(cls), &methodCount);

      for (unsigned int i = 0; i < methodCount; i++) {
        Method method = methods[i];
        SEL selector = method_getName(method);
        if ([NSStringFromSelector(selector) hasPrefix:@"__rct_export__"]) {
          IMP imp = method_getImplementation(method);
          auto exportedMethod = ((const RCTMethodInfo *(*)(id, SEL))imp)(_moduleClass, selector);
          id<RCTBridgeMethod> moduleMethod = [[RCTModuleMethod alloc] initWithExportedMethod:exportedMethod
                                                                                 moduleClass:_moduleClass];
          [moduleMethods addObject:moduleMethod];
        }
      }

      free(methods);
      cls = class_getSuperclass(cls);
    }

    _methods = [moduleMethods copy];
  }
  return _methods;
}

- (void)gatherConstants
{
  if (_hasConstantsToExport && !_constantsToExport) {
    RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, ([NSString stringWithFormat:@"[RCTModuleData gatherConstants] %@", _moduleClass]), nil);
    (void)[self instance];
    if (_requiresMainQueueSetup) {
      if (!RCTIsMainQueue()) {
        RCTLogWarn(@"Required dispatch_sync to load constants for %@. This may lead to deadlocks", _moduleClass);
      }

      RCTUnsafeExecuteOnMainQueueSync(^{
        self->_constantsToExport = [self->_instance constantsToExport] ?: @{};
      });
    } else {
      _constantsToExport = [_instance constantsToExport] ?: @{};
    }
    RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
  }
}

- (NSDictionary<NSString *, id> *)exportedConstants
{
  [self gatherConstants];
  NSDictionary<NSString *, id> *constants = _constantsToExport;
  _constantsToExport = nil; // Not needed anymore
  return constants;
}

- (dispatch_queue_t)methodQueue
{
  (void)[self instance];
  RCTAssert(_methodQueue != nullptr, @"Module %@ has no methodQueue (instance: %@, bridge.valid: %d)",
            self, _instance, _bridge.valid);
  return _methodQueue;
}

- (void)invalidate
{
  _methodQueue = nil;
}

- (NSString *)description
{
  return [NSString stringWithFormat:@"<%@: %p; name=\"%@\">", [self class], self, self.name];
}

@end