Sketch spline through points creation and relative functions API Sample

import adsk.core, adsk.fusion, traceback

def run(context):
    ui = None
    try: 
        app = adsk.core.Application.get()
        ui = app.userInterface

        doc = app.documents.add(adsk.core.DocumentTypes.FusionDesignDocumentType)
        design = app.activeProduct

        # Get the root component of the active design.
        rootComp = design.rootComponent

        # Create a new sketch on the xy plane.
        sketch = rootComp.sketches.add(rootComp.xYConstructionPlane)

        # Create an object collection for the points.
        points = adsk.core.ObjectCollection.create()

        # Define the points the spline with fit through.
        points.add(adsk.core.Point3D.create(0, 0, 0))
        points.add(adsk.core.Point3D.create(5, 1, 0))
        points.add(adsk.core.Point3D.create(6, 4, 3))
        points.add(adsk.core.Point3D.create(7, 6, 6))
        points.add(adsk.core.Point3D.create(2, 3, 0))
        points.add(adsk.core.Point3D.create(0, 1, 0))

        # Create the spline.
        spline = sketch.sketchCurves.sketchFittedSplines.add(points)

        # Get spline fit points
        fitPoints = spline.fitPoints
        
        # Get the second fit point
        fitPoint = fitPoints.item(1)
        
        # If there is no the relative tangent handle, activate the tangent handle
        line = spline.getTangentHandle(fitPoint)
        if line is None:
             line = spline.activateTangentHandle(fitPoint)
                
        # Get the tangent handle           
        gottenLine = spline.getTangentHandle(fitPoint)
        
        # Delete the tangent handle
        gottenLine.deleteMe()

        # Activate the curvature handle
        # If the curvature handle activated. the relative tangentHandle is activated automatically
        activatedArc= spline.activateCurvatureHandle(fitPoint)
        
        # Get curvature handle and tangent handle
        gottenArc= spline.getCurvatureHandle(fitPoint)
        gottenLine = spline.getTangentHandle(fitPoint)
        
        # Delete curvature handle
        gottenArc.deleteMe();

    except:
        if ui:
            ui.messageBox('Failed:\n{}'.format(traceback.format_exc()))

#include <Core/Application/Application.h>
#include <Core/Application/Documents.h>
#include <Core/Application/Document.h>
#include <Core/Application/Product.h>
#include <Core/Application/ObjectCollection.h>
#include <Core/UserInterface/UserInterface.h>
#include <Core/Geometry/Point3D.h>
#include <Fusion/Fusion/Design.h>
#include <Fusion/Components/Component.h>
#include <Fusion/Sketch/Sketch.h>
#include <Fusion/Sketch/Sketches.h>
#include <Fusion/Sketch/SketchCurves.h>
#include <Fusion/Sketch/SketchFittedSplines.h>
#include <Fusion/Sketch/SketchFittedSpline.h>
#include <Fusion/Sketch/SketchPointList.h>
#include <Fusion/Sketch/SketchPoint.h>
#include <Fusion/Sketch/SketchLine.h>
#include <Fusion/Sketch/SketchArc.h>
#include <Fusion/Construction/ConstructionPlane.h>

using namespace adsk::core;
using namespace adsk::fusion;

Ptr<UserInterface> ui;

extern "C" XI_EXPORT bool run(const char* context)
{
    Ptr<Application> app = Application::get();
    if (!app)
        return false;

    ui = app->userInterface();
    if (!ui)
        return false;

    Ptr<Documents> documents = app->documents();
    if (!documents)
        return false;

    Ptr<Document> doc = documents->add(DocumentTypes::FusionDesignDocumentType);
    if (!doc)
        return false;

    Ptr<Product> product = app->activeProduct();
    if (!product)
        return false;

    Ptr<Design> design = product;
    if (!design)
        return false;

    // Get the root component.
    Ptr<Component> rootComp = design->rootComponent();
    if (!rootComp)
        return false;

    // Create a new sketch on the xy plane.
    Ptr<Sketches> sketches = rootComp->sketches();
    if (!sketches)
        return false;
    Ptr<ConstructionPlane> xyPlane = rootComp->xYConstructionPlane();
    if (!xyPlane)
        return false;
    Ptr<Sketch> sketch = sketches->add(xyPlane);
    if (!sketch)
        return false;

    // Create an object collection for the points.
    Ptr<ObjectCollection> points = ObjectCollection::create();
    if (!points)
        return false;

    // Define the points the spline with fit through.
    points->add(Point3D::create(0, 0, 0));
    points->add(Point3D::create(5, 1, 0));
    points->add(Point3D::create(6, 4, 3));
    points->add(Point3D::create(7, 6, 6));
    points->add(Point3D::create(2, 3, 0));
    points->add(Point3D::create(0, 1, 0));

    // Create the spline.
    Ptr<SketchCurves> sketchCurves = sketch->sketchCurves();
    if (!sketchCurves)
        return false;
    Ptr<SketchFittedSplines> splines = sketchCurves->sketchFittedSplines();
    if (!splines)
        return false;

    Ptr<SketchFittedSpline> spline = splines->add(points);
    if (!spline)
        return false;

    // Get spline fit points
    Ptr<SketchPointList> fitPoints = spline->fitPoints();
    if (!fitPoints)
        return false;

    // Get the second fit point
    Ptr<SketchPoint> fitPoint = fitPoints->item(1);
    if (!fitPoint)
        return false;

    // If there is no the relative tangent handle, activate the tangent handle
    Ptr<SketchLine> line = spline->getTangentHandle(fitPoint);
    if (line)
        return false;
    else
    {
        line = spline->activateTangentHandle(fitPoint);
        if (!line)
            return false;
    }

    // Get the tangent handle
    Ptr<SketchLine> gottenLine = spline->getTangentHandle(fitPoint);
    if (!gottenLine)
        return false;

    // Delete the tangent handle
    bool isSuccess = gottenLine->deleteMe();
    if (!isSuccess)
        return false;

    // Activate the curvature handle
    // If the curvature handle activated. the relative tangentHandle is activated automatically
    Ptr<SketchArc> activatedArc = spline->activateCurvatureHandle(fitPoint);
    if (!activatedArc)
        return false;

    // Get curvature handle and tangent handle
    Ptr<SketchArc> gottenArc = spline->getCurvatureHandle(fitPoint);
    if (!gottenArc)
        return false;

    gottenLine = spline->getTangentHandle(fitPoint);
    if (!gottenLine)
        return false;

    // Delete curvature handle
    bool isDeleted = gottenArc->deleteMe();
    if (!isDeleted)
        return false;


    return true;
}

#ifdef XI_WIN

#include <windows.h>

BOOL APIENTRY DllMain(HMODULE hmodule, DWORD reason, LPVOID reserved)
{
    switch (reason)
    {
    case DLL_PROCESS_ATTACH:
    case DLL_THREAD_ATTACH:
    case DLL_THREAD_DETACH:
    case DLL_PROCESS_DETACH:
        break;
    }
    return TRUE;
}

#endif // XI_WIN