cvPosCmd.cpp
#include <maya/MPxCommand.h>
#include <maya/MStatus.h>
#include <maya/MArgList.h>
#include <maya/MFnPlugin.h>
#include <maya/MObject.h>
#include <maya/MGlobal.h>
#include <maya/MDagPath.h>
#include <maya/MItSelectionList.h>
#include <maya/MSelectionList.h>
#include <maya/MString.h>
#include <maya/MPoint.h>
#include <maya/MItCurveCV.h>
#include <maya/MItSurfaceCV.h>
#include <maya/MItMeshVertex.h>
#include <maya/MIOStream.h>
class cvPos : public MPxCommand
{
public:
                cvPos();
    virtual     ~cvPos();
    MStatus     doIt ( const MArgList& args );
    MStatus     redoIt ();
    MStatus     undoIt ();
    bool        isUndoable() const;
    static      void* creator();
private:
    MPoint      point;
};
cvPos::cvPos() :
    point(0.0, 0.0, 0.0)
{
}
cvPos::~cvPos() {}
void* cvPos::creator()
{
    return new cvPos;
}
bool cvPos::isUndoable() const
{
    return true;
}
MStatus cvPos::undoIt()
{
    return MS::kSuccess;
}
MStatus cvPos::doIt( const MArgList& args )
{
    MString componentName;
        MSpace::Space transformSpace = MSpace::kWorld;
        for (unsigned int i = 0; i < args.length (); i++)
        {
                MString argStr;
                args.get (i, argStr);
                if (MString ("-l") == argStr || MString ("-local") == argStr)
                        transformSpace = MSpace::kObject;
                else if (MString ("-w") == args.asString (i) ||
                                 MString ("-world") == argStr)
                        transformSpace = MSpace::kWorld;
                else
                        componentName = argStr;
        }
    MObject     component;
    MDagPath    dagPath;
        if (!componentName.length ()) {
                MSelectionList activeList;
                MGlobal::getActiveSelectionList (activeList);
                MItSelectionList iter (activeList, MFn::kComponent);
                if (iter.isDone ())     {
                        displayError ("No components selected");
                        return MS::kFailure;
                } else {
                        iter.getDagPath (dagPath, component);
                        iter.next ();
                        if (!iter.isDone ()) {
                                displayError ("More than one component is selected");
                                return MS::kFailure;
                        }
                }
        } else {
                MSelectionList list;
                if (! list.add( componentName ) ) {
                        componentName += ": no such component";
                        displayError(componentName);
                        return MS::kFailure; 
                }
                MItSelectionList iter( list );
        iter.getDagPath( dagPath, component );
        }
        if (component.isNull()) {
                displayError("not a component");
                return MS::kFailure;
        }
        switch (component.apiType()) {
        case MFn::kCurveCVComponent:
                {
                        MItCurveCV curveCVIter( dagPath, component );
                        point = curveCVIter.position(transformSpace );
                        curveCVIter.next();
                        if (!curveCVIter.isDone()) {
                                displayError ("More than one component is selected");
                                return MS::kFailure;
                        }
                        break;
                }
        case MFn::kSurfaceCVComponent:
                {
                        MItSurfaceCV surfCVIter( dagPath, component, true );
                        point = surfCVIter.position(transformSpace );
                        surfCVIter.next();
                        if (!surfCVIter.isDone()) {
                                displayError ("More than one component is selected");
                                return MS::kFailure;
                        }
                        break;
                }
        case MFn::kMeshVertComponent:
                {
                        MItMeshVertex vertexIter( dagPath, component );
                        point = vertexIter.position(transformSpace );
                        vertexIter.next();
                        if (!vertexIter.isDone()) {
                                displayError ("More than one component is selected");
                                return MS::kFailure;
                        }
                        break;
                }
        default:
                cerr << "Selected unsupported type: (" << component.apiType()
                         << "): " << component.apiTypeStr() << endl;
        }
    return redoIt();
}
MStatus cvPos::redoIt()
{
    clearResult();
    appendToResult( point.x );
    appendToResult( point.y );
    appendToResult( point.z );
    return MS::kSuccess;
}
MStatus initializePlugin( MObject obj )
{
        MStatus   status;
    MFnPlugin plugin( obj, PLUGIN_COMPANY, "3.0", "Any");
    status = plugin.registerCommand( "cvPos", cvPos::creator );
        if (!status) {
                status.perror("registerCommand");
                return status;
        }
    return status;
}
MStatus uninitializePlugin( MObject obj )
{
        MStatus   status;
    MFnPlugin plugin( obj );
    status = plugin.deregisterCommand( "cvPos" );
        if (!status) {
                status.perror("deregisterCommand");
                return status;
        }
    return status;
}