react native 0.50 源碼解析 再出發 持續更新

1.核心類

1.1 RCTRootView

一個RCTRootView持有一個RCTBridge成員變量

RCTRootView : UIView
  RCTBridge *bridge;
  UIViewController *reactViewController;
  UIView *contentView;
  UIView *loadingView;

1.2 RCTBridge

一個RCTBridge持有一個RCTCxxBridge成員變量

RCTBridge.h
 @interface RCTBridge : NSObject <RCTInvalidating>

RCTBridge+Private.h
@interface RCTBridge ()
   RCTBridge *batchedBridge;
@end

RCTBridge.m
- (Class)bridgeClass
  return [RCTCxxBridge class];

- (void)setUp
  Class bridgeClass = self.bridgeClass;
  self.batchedBridge = [[bridgeClass alloc] initWithParentBridge:self];
  [self.batchedBridge start];

1.3 RCTCxxBridge

RCTCxxBridge繼承自RCTBridge，是RCTBridge的一個變量，擁有弱引用parentBridge指向RCTBridge變量

RCTBridge+Private.h
@interface RCTCxxBridge:RCTBridge

RCTCxxBridge.mm
@interface RCTCxxBridge()
RCTBridge *parentBridge;
@end
//@interface ViewController()後面 ，@end前面的是類擴展，就是創建本類中似有的屬性和方法。其他類不能使用的

2.核心流程

2.1 native註冊模塊表

一個native類需要向js暴露的過程，就是向全局靜態數組RCTModuleClasses註冊自身class的過程。工程啓動後，自動生成全局靜態數組RCTModuleClasses，儲存註冊的class

######RCTBridge
聲明全局靜態數組：
static NSMutableArray<Class> *RCTModuleClasses;

######native類
需要做到以下兩點，
1.實現RCTBridgeModule協議
2.在m文件中放置RCT_EXPORT_MODULE()代碼。

RCT_EXPORT_MODULE宏給native類置入load函數。native類在加載過程中，可以自動向RCTModuleClasses註冊自身Class。實例如下

ClassA.h
#import <React/RCTBridgeModule.h>
@interface ClassA <RCTBridgeModule>
@end

ClassA.m
RCT_EXPORT_MODULE() ==>
extern __attribute__((visibility("default"))) 
void RCTRegisterModule(Class);  
+ (void)load { RCTRegisterModule(self); }

========================================
宏定義
RCTBridgeModule.h
#define RCT_EXPORT_MODULE(js_name) \
RCT_EXTERN void RCTRegisterModule(Class); \
+ (NSString *)moduleName { return @#js_name; } \
+ (void)load { RCTRegisterModule(self); }

#define RCT_EXPORT_MODULE(js_name) RCT_EXTERN void RCTRegisterModule(Class);  + (NSString *)moduleName { return @#js_name; }  + (void)load { RCTRegisterModule(self); }

RCTDefindes.h
#define RCT_EXTERN extern __attribute__((visibility("default")))

註冊
RCTBridge.m
static NSMutableArray<Class> *RCTModuleClasses;
void RCTRegisterModule(Class moduleClass)
   [RCTModuleClasses addObject:moduleClass];

2.2 RCTCxxBridge初始化模塊表

RCTCxxBridge有三個成員變量，_moduleDataByName，_moduleDataByID，_moduleClassesByID

RCTCxxBridge
NSMutableDictionary<NSString *, RCTModuleData *> *_moduleDataByName; //字典，name：RCTModuleData鍵值對
NSMutableArray<RCTModuleData *> *_moduleDataByID; //RCTModuleData數組
NSMutableArray<Class> *_moduleClassesByID; //Class數組
- (void)start 
  [self _initModules:RCTGetModuleClasses() withDispatchGroup:prepareBridge lazilyDiscovered:NO];

- (void)_initModules:(NSArray<id<RCTBridgeModule>> *)modules
   withDispatchGroup:(dispatch_group_t)dispatchGroup
    lazilyDiscovered:(BOOL)lazilyDiscovered
  NSArray<RCTModuleData *> *moduleDataById = [self registerModulesForClasses:modules]; //將modules轉換成RCTCxxBridge的模塊組

- (NSArray<RCTModuleData *> *)registerModulesForClasses:(NSArray<Class> *)moduleClasses
   for (Class moduleClass in moduleClasses) {
      _moduleDataByName[moduleName] = moduleData;
      [_moduleClassesByID addObject:moduleClass];
      [moduleDataByID addObject:moduleData];
   }
   [_moduleDataByID addObjectsFromArray:moduleDataByID];

2.3 RCTCxxBridge 加載/執行JS資源

 - (void)start 
     [self loadSource:^(NSError *error, RCTSource *source)
           {sourceCode = source.data;}]  // 加載JS
     [strongSelf executeSourceCode:sourceCode sync:NO]; //執行JS

- (void)loadSource:(RCTSourceLoadBlock)_onSourceLoad onProgress:(RCTSourceLoadProgressBlock)onProgress
     發送通知RCTBridgeWillDownloadScriptNotification
     RCTSourceLoadBlock onSourceLoad = ^(NSError *error, RCTSource *source) 
     {
            發送通知RCTBridgeDidDownloadScriptNotification：RCTSource
     }
    [RCTJavaScriptLoader loadBundleAtURL:self.bundleURL onProgress:onProgress onComplete:^(NSError *error, RCTSource *source)
     {
          onSourceLoad(error, source);
     }

- (void)executeSourceCode:(NSData *)sourceCode sync:(BOOL)sync
   - (void)executeApplicationScript:(NSData *)script
                             url:(NSURL *)url
                           async:(BOOL)async
  dispatch_block_t completion = ^{
          [self _flushPendingCalls];
          廣播通知RCTJavaScriptDidLoadNotification
          [self ensureOnJavaScriptThread:^{
             [self->_displayLink addToRunLoop:[NSRunLoop currentRunLoop]];
          }];
     }

- (void)executeApplicationScript:(NSData *)script
                             url:(NSURL *)url
                           async:(BOOL)async
  if (isRAMBundle(script))
      self->_reactInstance->loadRAMBundle(std::move(registry), std::move(scriptStr),
                                            sourceUrlStr.UTF8String, !async);
  else if (self->_reactInstance)
      self->_reactInstance->loadScriptFromString(std::make_unique<NSDataBigString>(script),
                                                 sourceUrlStr.UTF8String, !async);

- (void)registerAdditionalModuleClasses:(NSArray<Class> *)modules
    |=== - (NSArray<RCTModuleData *> *)registerModulesForClasses:(NSArray<Class> *)moduleClasses
          |---for (Class moduleClass in moduleClasses) 
          {
              NSString *moduleName = RCTBridgeModuleNameForClass(moduleClass);
              moduleData = [[RCTModuleData alloc] initWithModuleClass:moduleClass bridge:self];

          }

[RCTCxxBridge registerExtraModules]

• (void)start
  |--- 廣播通知---
  RCTJavaScriptWillStartLoadingNotification：@{@"bridge": self}
  |--- 新建並啓動js線程 _jsThread
  |--- 註冊moduleClass---
  [self registerExtraModules];
  [self _initModules:RCTGetModuleClasses() withDispatchGroup:prepareBridge lazilyDiscovered:NO];
  |--- 創建工廠並配置---
  std::shared_ptr<JSExecutorFactory> executorFactory;
  |--- 加載js資源---
  [self loadSource:^(NSError error, RCTSource source)
  |--- 執行js---
  [strongSelf executeSourceCode:sourceCode sync:NO];

啓動

[AppDelegate didFinishLaunchingWithOptions]
|---獲取jsCodeLocation
|---[RCTRootView initWithBundleURL..]
    |---[RCTBridge alloc+init]
        |---設置變量：delegate，bundleURL，moduleProvider, launchOptions
        |---[RCTBridge setUp]
            |---設置變量：bundleURL
            |---[RCTCxxBridge alloc+init]  --> RCTBridge.batchedBridge
            |---[RCTCxxBridge start]

    |---[RCTRootView initWithBridge:...]
          |---註冊三個通知，如下
          |---[self bundleFinishedLoading:([_bridge batchedBridge] ?: _bridge)];
                |---RCTRootContentView alloc
                |---[self runApplication:bridge];
                       |---[bridge enqueueJSCall:@"AppRegistry"
                 method:@"runApplication"
                   args:@[moduleName, appParameters]
             completion:NULL];
                |---insertSubview:_contentView

RCTRootView 繼承自UIView，內含RCTBridge變量，初始化參數BundleURL/moduleName/Properties/launchOptions。初始化的時候，初始化RCTBridge變量，自我初始化。自我初始化過程：註冊三個通知，RCTJavaScriptWillStartLoadingNotification/RCTJavaScriptDidLoadNotification/RCTContentDidAppearNotification

RCTBridge native call js

[RCTBridge enqueueJSCall:(NSString *)module method:(NSString *)method args:(NSArray *)args completion:(dispatch_block_t)completion]
|---[self.batchedBridge enqueueJSCall:module method:method args:args completion:completion];

RCTCxxBridge 成員：
_moduleClassesByID
_moduleDataByID
_moduleDataByName 可變字典：string（moduleName）：RCTModuleData（Data）的鍵值隊
RCTCxxBridge native call js,可以從任意線程中調起

RCTBridge  
- (void)setUp
   URL轉換
   self.batchedBridge = [[bridgeClass alloc] initWithParentBridge:self];
   [self.batchedBridge start];

- (void)registerAdditionalModuleClasses:(NSArray<Class> *)modules
   [self.batchedBridge registerAdditionalModuleClasses:modules];

RCTJavaScriptLoader  
+ (void)loadBundleAtURL:(NSURL *)scriptURL onProgress:(RCTSourceLoadProgressBlock)onProgress onComplete:(RCTSourceLoadBlock)onComplete
|---NSData *data = [self attemptSynchronousLoadOfBundleAtURL:scriptURL
                                          runtimeBCVersion:JSNoBytecodeFileFormatVersion
                                              sourceLength:&sourceLength
                                                     error:&error];
|---onComplete(nil, RCTSourceCreate(scriptURL, data, sourceLength));

+ (NSData *)attemptSynchronousLoadOfBundleAtURL:(NSURL *)scriptURL
                               runtimeBCVersion:(int32_t)runtimeBCVersion
                                   sourceLength:(int64_t *)sourceLength
                                          error:(NSError **)error
|---FILE *bundle = fopen(scriptURL.path.UTF8String, "r");
    size_t readResult = fread(&header, sizeof(header), 1, bundle);

[RCTCxxBridge enqueueJSCall:(NSString *)module method:(NSString *)method args:(NSArray *)args completion:(dispatch_block_t)completion]
|---

NSInvocation 調用 native 方法

調用原生代碼生成UI控件

RCTUIManager RCT_EXPORT_METHOD(createView:(nonnull NSNumber *)reactTag
                                 viewName:(NSString *)viewName
                                  rootTag:(nonnull NSNumber *)rootTag
                                    props:(NSDictionary *)props)
|---createViewBlock
      |---[RCTComponentData createViewWithTag:reactTag];
            |--- [self.manager view]   
                 #此處self.manager是實際需要生成的UI類，如RCTTextView等
                 #所以，所有RN的原生UI都必須實現view功能
      |---RCTUIManager->_viewRegistry[reactTag] = preliminaryCreatedView;  
          #保存至註冊數組，reactTag：preliminaryCreatedView
          #RCTUIManager->_viewRegistry 
          # {1 = "<RCTRootContentView: 0x7faf12c015d0; reactTag: 1; frame = (0 0; 414 736); gestureRecognizers = <NSArray: 0x60000024eaf0>; layer = <CALayer: 0x6040002376c0>>";
          # 2 = "<UIView: 0x7faf12f0a6d0; frame = (0 0; 0 0); layer = <CALayer: 0x600000621300>>";}

Instance C++ 類
void Instance::loadRAMBundle(std::unique_ptr<RAMBundleRegistry> bundleRegistry,
                             std::unique_ptr<const JSBigString> startupScript,
                             std::string startupScriptSourceURL,
                             bool loadSynchronously)

RCTModuleMethod C++ 類
通過NSInvocation動態調用相應的OC模塊方法

- (id)invokeWithBridge:(RCTBridge *)bridge
                module:(id)module
             arguments:(NSArray *)arguments
   [self processMethodSignature];   //set blocks 
   block(bridge, index, RCTNilIfNull(json(arguments))   //set arguments
   [_invocation invokeWithTarget:module];   //調起函數
   [_invocation getReturnValue:&returnValue];   //獲取返回值

RN 支持功能
tabbar，nagigator，text，image，數據庫？，ar？，真機調試日誌？，網絡，攝像頭拍照，圖片剪裁，音頻，視頻，下載，

添加RN庫

tabbar
官方組件 TabBarIOS,TabBarIOS.Item,只支持iOS，棄用
流行組件