Using map with enum e class members - c++

Question

Ok, I have the following class:
class Shader {
public:
...
private:
GLuint _vertexShader;
GLuint _fragmentShader;
}
Is it possible to create a mapping between enums(GL_VERTEX_SHADER, GL_FRAGMENT_SHADER) and the variables I declared in the class?
The reson for this is that I want to generalize a method that I am creating for this class.
switch ( shaderType )
{
case GL_VERTEX_SHADER:
_vertexShader = glCreateShader( shaderType );
glShaderSource( _vertexShader, 1, &shaderCode, 0 );
glCompileShader( _vertexShader );
glGetShaderiv( _vertexShader, GL_COMPILE_STATUS, &isCompiled );
break;
case GL_FRAGMENT_SHADER:
_fragmentShader = glCreateShader( shaderType );
glShaderSource( _fragmentShader, 1, &shaderCode, 0 );
glCompileShader( _fragmentShader );
glGetShaderiv( _fragmentShader, GL_COMPILE_STATUS, &isCompiled );
break;
}
As you can see from this code, I have to do a switch to do basically the same code, but with just the variable changing. So it would be a lot nicer if I could instead of using switch, mapping the GLenum with the respective variable.

Answer 1

Direct answer:
you could make a mapping from an enum to a pointer to data member:
std::map<GLenum, GLuint Shader::*> mapper;
mapper[GL_VERTEX_SHADER ] = &Shader::_vertexShader;
mapper[GL_FRAGMENT_SHADER] = &Shader::_fragmentShader;
or, if the enum id's have values 0 and 1:
std::vector<GLuint Shader::*> mapper(2);
mapper[GL_VERTEX_SHADER ] = &Shader::_vertexShader;
mapper[GL_FRAGMENT_SHADER] = &Shader::_fragmentShader;
Then you just factor out the common code by parameterization of type GLuint&.
template <typename SC, typename Bool>
void CreateShader(GLuint& shader, GLenum shaderType, SC& shaderCode, Bool& isCompiled)
{
shader = glCreateShader( shaderType );
glShaderSource( shader, 1, &shaderCode, 0 );
glCompileShader( shader );
glGetShaderiv( shader, GL_COMPILE_STATUS, &isCompiled );
}
And then:
CreateShader(this->*mapper[shaderType], shaderType, shaderCode, isCompiled);
But for this example I would just use a switch and not define, initialize and use the (global?) mapper object:
switch ( shaderType )
{
case GL_VERTEX_SHADER:
CreateShader(_vertexShader, shaderType, shaderCode, isCompiled);
break;
case GL_FRAGMENT_SHADER:
CreateShader(_fragmentShader, shaderType, shaderCode, isCompiled);
break;
}