Using Lambdas in C++: Listing 2

Function objects in C++.

// SaveFunction object as an interface.
// Interfaces in C++ are conceptual. It's not that they don't exist, but they are a special
// case of abstract classes whose methods are all pure virtual (declared as "=0" and
// therefore not defined.
class SaveFunction
{
public:
  virtual int operator()(Image image, string filepath) =0;
};

class SaveAsPNG : SaveFunction
{
public:
  int operator()(Image image, string filepath)
  {
    ...
  }
};

class SaveAsGIF : SaveFunction
{
public:
  int operator()(Image image, string filepath)
  {
    ...
  }
};

class SaveAsTIFF : SaveFunction
{
public:
  int operator()(Image image, string filepath)
  {
    ...
  }
};

class SaveAsJPG : public SaveFunction
{
public:
  int operator()(Image image, string filepath)
  {
    ...
  }
};

// These two lines instance the JPG functor and invoke it.
SaveAsJPG saveFunction;
saveFunction(im, "my_image");

About the Author

Diego Dagum is a software architect and developer with more than 20 years of experience. He can be reached at email@diegodagum.com.