c++ - C to C++ 转换杂项声明

Question

要转换的代码:

struct CurrentFrameCloudView
{
  CurrentFrameCloudView() : cloud_device_ (480, 640), cloud_viewer_ ("Frame Cloud Viewer")
  {
    cloud_ptr_ = PointCloud<PointXYZ>::Ptr (new PointCloud<PointXYZ>);

    cloud_viewer_.setBackgroundColor (0, 0, 0.15);
    cloud_viewer_.setPointCloudRenderingProperties (visualization::PCL_VISUALIZER_POINT_SIZE, 1);
    cloud_viewer_.addCoordinateSystem (1.0);
    cloud_viewer_.initCameraParameters ();
    cloud_viewer_.setPosition (0, 500);
    cloud_viewer_.setSize (640, 480);
    cloud_viewer_.setCameraClipDistances (0.01, 10.01);
  }

  void
  show (const KinfuTracker& kinfu)
  {
    kinfu.getLastFrameCloud (cloud_device_);

    int c;
    cloud_device_.download (cloud_ptr_->points, c);
    cloud_ptr_->width = cloud_device_.cols ();
    cloud_ptr_->height = cloud_device_.rows ();
    cloud_ptr_->is_dense = false;

    cloud_viewer_.removeAllPointClouds ();
    cloud_viewer_.addPointCloud<PointXYZ>(cloud_ptr_);
    cloud_viewer_.spinOnce ();
  }

  void
  setViewerPose (const Eigen::Affine3f& viewer_pose) {
    ::setViewerPose (cloud_viewer_, viewer_pose);
  }

  PointCloud<PointXYZ>::Ptr cloud_ptr_;
  DeviceArray2D<PointXYZ> cloud_device_;
  visualization::PCLVisualizer cloud_viewer_;
};

问题:

谁能给我解释一下这行代码？

void
setViewerPose (const Eigen::Affine3f& viewer_pose) {
        ::setViewerPose (cloud_viewer_, viewer_pose); // especially here ...
}

欢迎任何帮助!

Answer 1

::setViewerPose (cloud_viewer_, viewer_pose);

此行调用全局函数 setViewerPose()。双冒号 :: 确保它调用全局命名空间中的函数而不是当前类中的函数。

通常，:: 用于访问命名空间成员，如 std::cout，或静态类成员，如 MySingleton::instance。如果您在左侧省略命名空间/类名，那么它会访问全局项。