[React Native] 在 iOS 中，关于 ViewCo

1. 创建或找到一个现成的 BridgeModule 类
2. 在该 BridgeModule 类的 .m 文件中，确保包含

 #import "UIView+React.h"

3. 在 @implementation 中，确保包含

 @synthesize bridge = _bridge;

4. 在 @implementation 中，RCT_EXPORT_METHOD 一个 Bridge 方法

 RCT_EXPORT_METHOD(
   sometingToDoWithTheViewControllerOfTheComponent:(nonnull NSNumber *)reactTag // Component 对象的 reactTag
   resolver:(RCTPromiseResolveBlock)resolve // 这行 
   rejecter:(RCTPromiseRejectBlock)reject   // 和这行是可选的，如果需要在执行完毕后给 JavaScript 通知的话，就带上
 )
 {
   // 实现后文详述
 }

5. 在 Bridge 方法中，通过如下代码取得 reactTag 对应的 view，并基于该 view 取得它所对应的 viewController

 RCTUIManager *uiManager = _bridge.uiManager;
 dispatch_async(uiManager.methodQueue, ^{
   [uiManager addUIBlock:^(RCTUIManager *uiManager, NSDictionary<NSNumber *,UIView *> *viewRegistry) {
     UIView *view = viewRegistry[reactTag];
     UIViewController *viewController = (UIViewController *)view.reactViewController;
     // It's now ok to do something with the viewController
     // which is in charge of the component.
   }
 }

1. 基于上述办法取到当前 Component 所属的 ViewController
2. 通过如下代码取得它所属的 navigationController，调用它的 pushViewController 或 presentViewController 方法即可

 [viewController.navigationController pushViewController:anotherViewController animated:YES]; // 跳转
 [viewController.navigationController presentViewController:anotherViewController animated:YES completion:^{}] ;// 弹出

3. 完整代码如下：

 RCT_EXPORT_METHOD
 (
  pushViewControllerXYZ:(nonnull NSNumber *)reactTag
  resolver:(RCTPromiseResolveBlock)resolve
  rejecter:(RCTPromiseRejectBlock)reject
 )
 {
   RCTUIManager *uiManager = _bridge.uiManager;
   dispatch_async(uiManager.methodQueue, ^{
     [uiManager addUIBlock:^(RCTUIManager *uiManager, NSDictionary<NSNumber *,UIView *> *viewRegistry) {
       UIView *view = viewRegistry[reactTag];
       UIViewController *viewController = (UIViewController *)view.reactViewController;
       [viewController pushViewController:[ViewControllerXYZ new] animated:YES];
       resolve(nil);
     }
   }
 }

RCT_EXPORT_METHOD
(
  presentViewControllerXYZ:(nonnull NSNumber *)reactTag
  resolver:(RCTPromiseResolveBlock)resolve
  rejecter:(RCTPromiseRejectBlock)reject
)
{
  RCTUIManager *uiManager = _bridge.uiManager;
  dispatch_async(uiManager.methodQueue, ^{
    [uiManager addUIBlock:^(RCTUIManager *uiManager, NSDictionary<NSNumber *,UIView *> *viewRegistry) {
      UIView *view = viewRegistry[reactTag];
      UIViewController *viewController = (UIViewController *)view.reactViewController;
      [viewController presentViewController:[ViewControllerXYZ new] animated:YES completion:^{}];
      resolve(nil);
    }
  }
}

1. 基于上述办法取到当前 Component 所属的 ViewController
2. 通过如下代码取得它对应的 navigationItem，然后各个属性随便设

 viewController.navigationItem.title = @"Hello";
 viewController.navigationItem.prompt = @"Aloha";

3. 如果希望设置 navigationItem 的 titleView 为某个 React Native Component：

 RCT_EXPORT_METHOD
 (
  setTitleView:(nonnull NSNumber *)reactTag
  props:(NSDictionary *)props
  resolver:(RCTPromiseResolveBlock)resolve
  rejecter:(RCTPromiseRejectBlock)reject
 )
 {
   UIView *titleView = [[RCTRootView alloc] initWithBridge:_bridge
                                                moduleName:[props objectForKey:@"moduleName"]
                                         initialProperties:[props objectForKey:@"initialProperties"]];
   viewController.navigationItem.titleView = titleView;
 }

4. 如果希望设置 navigationItem 的 left、right、back 按钮：

1. ~