GetObjectProperty

This function gets the value(s) of a certain objectProperty in the context of an instance.
The value of card gives the actual card of the values list.
The list values of integers is a list of handles to instances, this list has a length as givin in the value card.
The return value always should be 0, if not something is wrong in the way this property is called.

Syntax

//
//   Strong typing definition
//
int64_t         GetObjectProperty(
                        OwlInstance             owlInstance,
                        OwlObjectProperty       owlObjectProperty,
                        const OwlInstance       ** values,
                        int64_t                 * card
                    );

static  inline  int64_t GetObjectProperty(
                                OwlInstance             owlInstance,
                                OwlObjectProperty       owlObjectProperty,
                                OwlInstance             ** values,
                                int64_t                 * card
                            )
{
    return  GetObjectProperty(
                    owlInstance,
                    owlObjectProperty,
                    (const OwlInstance**) values,
                    card
                );
}

static  inline  int64_t GetObjectProperty(
                                int64_t                 owlInstance,
                                int64_t                 owlObjectProperty
                            )
{
    OwlInstance * values = nullptr;
    int64_t     card = 0;

    GetObjectProperty(
            owlInstance,
            owlObjectProperty,
            &values,
            &card
        );

    if (card == 1)
        return  values[0];
    else
        return  0;
}


//
//   Weak typing definition
//
int64_t __declspec(dllexport) __stdcall GetObjectProperty(
                                                int64_t                 owlInstance,
                                                int64_t                 owlObjectProperty,
                                                const int64_t           ** values,
                                                int64_t                 * card
                                            );

static  inline  int64_t GetObjectProperty(
                                int64_t                 owlInstance,
                                int64_t                 owlObjectProperty,
                                int64_t                 ** values,
                                int64_t                 * card
                            )
{
    return  GetObjectProperty(
                    owlInstance,
                    owlObjectProperty,
                    (const OwlInstance**) values,
                    card
                );
}

static  inline  int64_t GetObjectProperty(
                                int64_t                 owlInstance,
                                int64_t                 owlObjectProperty
                            )
{
    OwlInstance * values = nullptr;
    int64_t     card = 0;

    GetObjectProperty(
            owlInstance,
            owlObjectProperty,
            &values,
            &card
        );

    if (card == 1)
        return  values[0];
    else
        return  0;
}
    

Property owlInstance

Size: 64 bit / 8 byte (value)
The handle to the specific instance in the design tree. The instance handle is static within one open model but is most probably different when the same instance is opened in another model. The instance is always exactly of one unique class.

Property owlObjectProperty

Size: 64 bit / 8 byte (value)
This attribute represents a handle to the object property (relation). The handle will be static during the life-time of the model, when the model (or part of it) is saved and opened again, the handle will most probably be different.

Property values

Size: 64 bit / 8 byte (reference)
The output array for object properties content. The contents memory is allocated by the library

Property card

Size: 64 bit / 8 byte (reference)
The cardinality (i.e. number of elements) of the array as given or returned.

Example (based on pure API calls)

Here you can find code snippits that show how the API call GetObjectProperty can be used.

#include    "./include/engine.h"
#include    <stdio.h>
#include    <string.h>

int64_t model = CreateModel();

if (model) {
    //
    //  Classes
    //
    int64_t classAbcd = CreateClass(model, "ABCD");

    //
    //  Object Properties (relations)
    //
    int64_t propertyAb = CreateProperty(model, OBJECTPROPERTY_TYPE, "Ab");

    //
    //  Instances
    //
    int64_t instanceAbcdI = CreateInstance(classAbcd, nullptr),
            instanceAbcdII = CreateInstance(classAbcd, nullptr);

    //
    //  Set Properties
    //
        
    {
        SetObjectProperty(instanceAbcdI, propertyAb, &instanceAbcdII, 1);

        int64_t valuesAb[3] = { instanceAbcdI, instanceAbcdII, instanceAbcdI };
        SetObjectProperty(instanceAbcdII, propertyAb, valuesAb, 3);
    }

    //
    //  Get Properties
    //

    {
        int64_t card = 0,
                * values = nullptr;
        GetObjectProperty(instanceAbcdI, propertyAb, &values, &card);

        assert(card == 1 && values[0] == instanceAbcdII);
    }

    {
        int64_t card = 0,
                * values = nullptr;
        GetObjectProperty(instanceAbcdII, propertyAb, &values, &card);

        assert(card == 3 && values[0] == instanceAbcdI && values[1] == instanceAbcdII && values[2] == instanceAbcdI);
    }

    //
    //  The same can be applied to existing classes and properties
    //

    //
    //  Classes
    //
    int64_t classCollection = GetClassByName(model, "Collection"),
            classCube = GetClassByName(model, "Cube");

    //
    //  Object Properties (relations)
    //
    int64_t propertyObjects = GetPropertyByName(model, "objects");

    //
    //  Datatype Properties (attributes)
    //
    int64_t propertyLength = GetPropertyByName(model, "length");

    //
    //  Instances (creating)
    //
    int64_t instanceCollectionI = CreateInstance(classCollection, nullptr),
            instanceCollectionII = CreateInstance(classCollection, nullptr),
            instanceCube = CreateInstance(classCube, nullptr);

    double  length = 1.0;
        
    SetDatatypeProperty(instanceCube, propertyLength, &length, 1);

    int64_t values[3] = { instanceCollectionII, instanceCube, instanceCube };
    SetObjectProperty(instanceCollectionI, propertyObjects, values, 3);
    SetObjectProperty(instanceCollectionII, propertyObjects, &instanceCube, 1);

    //
    //  CollectionI contains 3 cubes and CollectionII contains 1 cube
    //
    assert(GetVolume(instanceCollectionI, nullptr, nullptr) == 3);
    assert(GetVolume(instanceCollectionII, nullptr, nullptr) == 1);

    //
    //  The resulting model can be viewed in 3D-Editor.exe
    //
    SaveModel(model, "c:\\created\\myFile.bin");
    CloseModel(model);
}