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Class interrelations problems

Started by Overburn Dec 4, 2008 at 12:28 PM 6 replies 850+ views

Original Post

Dec 4, 2008 at 12:28 PM

Ok, so I have 2 classes: CZRoot and CZMesh in CZRoot i have a Render() function that needs pointers to CZMesh objects to render them. in CZMesh i have a loadMesh() function that uses the CZRoot D3D device. I have a problem. how do I give each class what they need? i have thought of inheritance but it wouldn't really be a good design choice. can anyone help me on this? :D

Antheus

216

Antheus

Dec 4, 2008 at 12:49 PM

// mesh.hpp// doesn't include root.hpp// forward declarationclass CZRoot;class CZMesh {  CZRoot * root;};

You can optionally do the same for other classes.

Overburn

Author

Overburn

Dec 4, 2008 at 1:20 PM

thanx :) it worked

Overburn

Author

Overburn

Dec 4, 2008 at 1:54 PM

erm.. of course..
but i need to pass a pointer the other way around too, and it' kindof a chicken and egg problem.

CZRoot* root = new CZRoot();
CZMesh* mesh = new CZMesh(root);

, so i try this:
root->meshobject=mesh;

but unfortunately it gives a runtime error. anyone have any idea please? :)

Mantear

Dec 4, 2008 at 2:18 PM

CZRoot* root = NULL;CZMesh* mesh = new CZMesh(root);root = new CZRoot(mesh);

Just make sure CZMesh does not try to use its CZRoot pointer in the constructor, as it'll still be NULL.

_goat

Dec 4, 2008 at 10:50 PM

Quote:
Original post by Mantear
CZRoot* root = NULL;CZMesh* mesh = new CZMesh(root);root = new CZRoot(mesh);
Just make sure CZMesh does not try to use its CZRoot pointer in the constructor, as it'll still be NULL.

It will still be null afterwards, too.

Refactor your design

Tight coupling like this is always a sign of wonky design. Try and find a way to design your code where these things do not need to know of each other. If such a link between two objects is necessity (ie, they have a relation with each other), then take a page out of the RDBMS book, and create a third class, which represents the relationship:

struct mesh_root_link{    mesh_root_link(Mesh* mesh, Root* root)        : mesh(mesh), root(root)    {    }    // accessors and functions that require the knowledge of both of these things go hereprivate:    Mesh* mesh;    Root* root;};

Overburn

Author

Overburn

Dec 4, 2008 at 10:56 PM

thanx :) it kinda worked..
but i also have this little problem... as in i am doing something wrong here:
g_pd3dDevice->SetMaterial( &meshobject->g_pMeshMaterials );

it's a runtime one also. :(

Overburn

Author

Overburn

Dec 4, 2008 at 11:11 PM

hmm, that's a good idea _goat. will try :) thanx

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