Complete implementation bridging to C++

RCTHelloWorld.m

// ./ios/ReactBridge/RCTHelloWorld.m
#import "RCTHelloWorld.h"
#import "HWHelloWorld.h"

@implementation RCTHelloWorld{
  HWHelloWorld *_cppApi;
}

- (RCTHelloWorld *)init
{
  self = [super init];
  _cppApi = [HWHelloWorld create];
  return self;
}

+ (BOOL)requiresMainQueueSetup
{
  return NO;
}

RCT_EXPORT_MODULE();

RCT_REMAP_METHOD(sayHello,
                 resolver:(RCTPromiseResolveBlock)resolve
                 rejecter:(RCTPromiseRejectBlock)reject)
{

  NSString *response = [_cppApi getHelloWorld];
  resolve(response);
}
@end