React Native 和 Objective C 委托

Question

我对原生代码和桥接机制与原生代码的反应非常陌生，尤其是当框架有委托时。假设我正在尝试连接以下框架：

@protocol BRPtouchNetworkDelegate;

@class PLNetworkModule;

@interface BRPtouchNetworkManager : NSObject <NSNetServiceBrowserDelegate,NSNetServiceDelegate>


@property(retain, nonatomic) NSMutableArray* registeredPrinterNames;
@property(assign, nonatomic) BOOL isEnableIPv6Search;


- (int)startSearch: (int)searchTime;
- (NSArray*)getPrinterNetInfo;

- (BOOL)setPrinterNames:(NSArray*)strPrinterNames;
- (BOOL)setPrinterName:(NSString*)strPrinterName;

- (id)initWithPrinterNames:(NSArray*)strPrinterNames;
- (id)initWithPrinterName:(NSString*)strPrinterName;

@property (nonatomic, assign) id <BRPtouchNetworkDelegate> delegate;

@end

@protocol BRPtouchNetworkDelegate <NSObject>

-(void) didFinishSearch:(id)sender;

@end

以下是我实现的桥接模块：

RCTBRPtouchNetworkManager.h

#import <React/RCTBridgeModule.h>
#import <BRPtouchPrinterKit/BRPtouchPrinterKit.h>

@interface RCTBRPtouchNetworkManager : NSObject <RCTBridgeModule, BRPtouchNetworkDelegate>
@end

RCTBRPtouchNetworkManager.m

#import "RCTBRPtouchNetworkManager.h"
#import <BRPtouchPrinterKit/BRPtouchPrinterKit.h>
#import <React/RCTLog.h>

@implementation RCTBRPtouchNetworkManager {
  BRPtouchNetworkManager  *_networkManager;
}

RCT_EXPORT_MODULE();

RCT_EXPORT_METHOD(addEvent:(NSString *)name location:(NSString *)location)
{
  RCTLogInfo(@"Pretending to create an event %@ at %@", name, location); //a dummy method to test the bridge
}

RCT_EXPORT_METHOD(startSearchWithTimeout:(int)time) {
  RCTLogInfo(@"Bridge started search with time %d", time);

  _networkManager = [[BRPtouchNetworkManager alloc] init];
  _networkManager.delegate = self; //I'm setting delegate here
  _networkManager.isEnableIPv6Search = NO;
  NSString *  path = [[NSBundle mainBundle] pathForResource:@"PrinterList" ofType:@"plist"];
  if( path )
  {
    NSDictionary *printerDict = [NSDictionary dictionaryWithContentsOfFile:path];
    NSArray *printerList = [[NSArray alloc] initWithArray:printerDict.allKeys];
    [_networkManager setPrinterNames:printerList];
  } else {
    RCTLogInfo(@"PrinterList path not found");
  }

  //  Start printer search
  [_networkManager startSearch: 5.0];

}

- (void)didFinishSearch:(id)sender {
  NSLog(@"didFinishedSearch"); //this delegate method is not called
}

@end

我可以轻松调用虚拟方法并在日志中查看结果。但是，从不调用委托方法 didFinishSearch()。我从 javascript 中调用它如下：

componentDidMount() {
    let networkManager = NativeModules.BRPtouchNetworkManager;
    networkManager.startSearchWithTimeout(5.0);
}

我有什么遗漏的吗？我是否正确实施委托？这种功能是否可能（似乎不可能，因为 iOS 社区长期使用委托方法）。非常感谢您的帮助。

编辑

我发现将以下内容添加到我的网桥管理器文件中会使委托触发（感谢this post）

- (dispatch_queue_t)methodQueue
{
    return dispatch_get_main_queue();
}

但是，尽管这解决了问题，但我希望对这里发生的事情有更技术性的了解，因为我似乎无法完全掌握它。谢谢

Answer 1

我知道这不是对帖子的回答，而是针对您要求更多技术理解的部分 - dispatch_get_main_queue();将委托方法响应放在主线程上。由于 JS 是单线程的，因此后台线程上的任何进程都不会对其可见。