check if a NewtonBody ptr still exists without crashing

[arkdemon]

Hello everyone .
I wanted to know how we can check if a NewtonBody* is valid / not destroyed. Whenever I call

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if(!body)//if body not destroyed

when "body" is destroyed or inexistant, my program crashes. (body is a NewtonBody* )

My newton version is 3.12 (the last one that works for me) so this issue might have been addressed already.

Thank you for your answers

[AntonSynytsia]

I wish there were such methods to check valididy, like:
NewtonIsWorldValid(world_ptr) and it would return 1 or 0.
NewtonIsBodyValid(body_ptr)
NewtonIsCollisonValid(collision_ptr)
etc...

But posting this once, Juleo suggested to use BodyDestructorCallback.
Here is the post: viewtopic.php?f=12&t=8509

[arkdemon]

I'm sure I checked the forum before but I didn't find anything. strange...
Anyway thank you for your answer
I'll do as you recommend

[FSA]

If newton provides such functions it would be a bit pointless. Newton is not responsible to check for valid bodies. The user should check it. Or what is your argument to have such functions?

[arkdemon]

Well I found a way using Newton: (didn't check if it works so it might have bugs - because I found it right now :3 )

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    bool ValidBody(NewtonWorld *w, NewtonBody *b){
        for(NewtonBody *_b = NewtonWorldGetFirstBody(w); _b; _b = NewtonWorldGetNextBody(w, _b)){
            if(b == _b) return true;
        }
        return false;
    }

If newton provides such functions it would be a bit pointless. Newton is not responsible to check for valid bodies

If you look at my function, you can see that Newton provides a way to do this :p (not sure if it is the best way to do it though)

[FSA]

You are just iterating over the list of bodies. These functions are 100% not for this usage

[AntonSynytsia]

You are just iterating over the list of bodies. These functions are 100% not for this usage

What do you mean its not 100% for this use?
It determines whether the specified body exists in the world... If it doesn't then false is returned, which means the body is not part of the current world and/or it's destroyed...

[JoeJ]

What he means ist most probably that it would be better to set a flag in the user data of a body before it is removed from the world, and clear it when the body is added to the world again.
Now you only need to look at the flag of the body instead of a loop.
Also you could add / remove the body (its user data) to a linked list to quickly find all disabled bodies.

[AntonSynytsia]

What he means ist most probably that it would be better to set a flag in the user data of a body before it is removed from the world, and clear it when the body is added to the world again.
Now you only need to look at the flag of the body instead of a loop.
Also you could add / remove the body (its user data) to a linked list to quickly find all disabled bodies.

The flag technique works too, and I think is the best solution. Although unlike the previous technique by arkdemon, this technique will require to use the destructor callback to determine when the body gets destroyed. There is nothing bad about the destructor callback, I'm just listing the requirements of both techniques.