Question

I create this struct:

struct MyBodyData
{
    int someNumber;
};

and then created a new body:

b2BodyDef bodyDef;
bodyDef.type = b2_dynamicBody;
bodyDef.position.Set(0.0f, -10.0f);
b2Body* body1 = world->CreateBody(&bodyDef);
MyBodyData *bodyData = new MyBodyData();
bodyData->someNumber = 4;
body1->SetUserData(&bodyData);

b2PolygonShape dynamicBox;
dynamicBox.SetAsBox(.5f, .5f);//These are mid points for our 1m box
b2FixtureDef fixtureDef;
fixtureDef.shape = &dynamicBox; 
fixtureDef.density = 1.0f;
fixtureDef.friction = 0.3f;
body1->CreateFixture(&fixtureDef);

And then tried to access someNumber here:

for (b2Body* b = world->GetBodyList(); b; b = b->GetNext())
{
    CCLOG(@"Hello One");
    MyBodyData* data = (MyBodyData*)b->GetUserData();
    if (data!=0 && data->someNumber != 0)
    {
        int temp;
        temp = data->someNumber;
        CCLOG(@"Hello Again! %d",temp);
    }
}

It displays someNumber as a memory address 6-7 digits long instead of the value “4”.

What am I missing?

Answer 1

body1->SetUserData(&bodyData);

You’re setting the body data to be the address of the pointer bodyData. You don’t want that, you want to set it to bodyData. So:

body1->SetUserData(bodyData);