Geometry cannot be cast Error

Troubleshooting General Help
1

Hi,



im working on a game where i can interact with objects, like i.e. trees. I already managed to load a wavefront .obj into my map with no problems:



[java]

private void addTreeTest(){

Geometry test = (Geometry) main.getAssetManager().loadModel("Models/test.obj");

System.out.println(main.getAssetManager().loadModel("Models/test.obj").getClass());

test.setLocalTranslation(20, getHeightAt(20, 20), 20);

test.scale(1, 1, 1);

node.attachChild(test);

RigidBodyControl testcon = new RigidBodyControl(CollisionShapeFactory.createMeshShape(test), 0);

test.addControl(testcon);

manager.getPhysic().getPhysicsSpace().add(testcon);

}

[/java]



But now i need to have attributes in that Geometry, like health to know when a tree is cut down. I created a class which extends Geometry

and inserted it into my code:



[java]

mygame.Objects.Object test = (mygame.Objects.Object) main.getAssetManager().loadModel("Models/test.obj");

[/java]



The mygame.Objects.Object class just extends the Geometry class, there is nothing else in it. But when i try to run the game i get:

Uncaught exception thrown in Thread[LWJGL Renderer Thread,5,main]

java.lang.ClassCastException: com.jme3.scene.Geometry cannot be cast to mygame.Objects.Object



thx for any help

2

This is an inheritance problem, the “is a” fundamental OOP feature. You have, Geometry → Object. An Object “is a” Geometry, but a Geometry is not an Object. Better to have a class which contains the Geometry using composition “has a”, and add all the features, life etc to that class, or use setUserdata(), to attach it directly to the spatial.

3

thx for the fast reply,



i didnt see the setuserdata, sounds like a good way. the other option is not so good, because i wanted to “get the nearest object on click”, and since i get a spatial from it, i cant hold the information in an external class which cant be attached to a node. ill try it with the user data, thx again

4

yeh setUserData/getUserData will definitely help you there. You should even be able to attach your “Object” to it.



[java]Object object = new Object();

object.setHealth(100);

spatial.setUserData(“object”, object);

Object object1 = (Object) spatial.getUserData(“object”);

object1.getHealth();

[/java]

etc…

5

works fine now for me. if anyone else is going to realize it in this way, the object which is given to the userdata must implement the savable interface.

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