加粗位置有一点点性能浪费，第二次加载同一个singleton实例的时候会取前一次保存的实例，这里就没必要再 alloc init了

[shuixin536]

加粗位置有一点点性能浪费，第二次加载同一个singleton实例的时候会取前一次保存的实例，这里就没必要再 alloc init了

• (id)createService:(Protocol *)service
  {
  id implInstance = nil;

  if (![self checkValidService:service] && self.enableException) {
  @throw [NSException exceptionWithName:NSInternalInconsistencyException reason:[NSString stringWithFormat:@"%@ protocol does not been registed", NSStringFromProtocol(service)] userInfo:nil];
  }

  Class implClass = [self serviceImplClass:service];

  if ([[implClass class] respondsToSelector:@selector(shareInstance)])
  implInstance = [[implClass class] shareInstance];
  else
  implInstance = [[implClass alloc] init];

  if (![implInstance respondsToSelector:@selector(singleton)]) {
  return implInstance;
  }

  NSString *serviceStr = NSStringFromProtocol(service);

  if ([implInstance singleton]) {
  id protocol = [[BHContext shareInstance] getServiceInstanceFromServiceName:serviceStr];

    if (protocol) {
        return protocol;
    } else {
        [[BHContext shareInstance] addServiceWithImplInstance:implInstance serviceName:serviceStr];
    }
  

  } else {
  [[BHContext shareInstance] addServiceWithImplInstance:implInstance serviceName:serviceStr];
  }

  return implInstance;
  }