How to use a C++ pointer of abstract type to point to a concrete class?

Question

I'm working with the Point Cloud Library and I'm trying to avoid repeating the following behaviour:

pcl::PointCloud<pcl::PointXYZRGB>::Ptr filter(PointCloud<pcl::PointXYZRGB>::Ptr input_cloud) {
    pcl::PointCloud<pcl::PointXYZRGB>::Ptr cloud_filtered(new pcl::PointCloud<pcl::PointXYZRGB>);
    subclass.setInputCloud(input_cloud);
    subclass.filter(*cloud_filtered);
    return cloud_filtered;
}

I hoped to use something based on this example and along the lines of:

pcl::Filter<PointXYZRGB>* f;
pcl::Subclass<PointXYZRGB> s; //where s is an implementation of f
f = &s;

pcl::PointCloud<pcl::PointXYZRGB>::Ptr filter(PointCloud<pcl::PointXYZRGB>::Ptr input_cloud) {
    pcl::PointCloud<pcl::PointXYZRGB>::Ptr cloud_filtered(new pcl::PointCloud<pcl::PointXYZRGB>);
    f->setInputCloud(input_cloud);
    f->filter(*cloud_filtered);
    return cloud_filtered;
}

However this will not compile as f does not name a type as reported by the compiler.

I assume is this due to pcl::Filter being an abstract class?

Is this approach valid for an example class such as pcl::VoxelGrid or is there an alternative?

Any help is much appreciated!

Answer 1

The line f = &s; should be moved to within a function.

In this case it was moved to within the constructors of derived subclasses.

Credit and thanks for the answer to user, aschepler