Re: Trouble binding a class - should be simple

On 05/05/2011 11:35, Tony Kostanjsek wrote:
> Have you tried to add a binding for the default constructor?
>
>
>
>
> On 05.05.2011, at 11:53, Simon Pickles <[email protected] 
> <mailto:[email protected]>> wrote:
>
>> On 05/05/2011 09:48, feng qiu wrote:
>>> Please try v*:*getX().
>>>
>>> On 5 May 2011 15:56, Simon Pickles <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>>
>>>
>>>     Hello,
>>>
>>>     I am trying to expose part of the btVector3 class from
>>>     BulletPhysics to Lua:
>>>
>>>     http://www.bulletphysics.com/Bullet/BulletFull/classbtVector3.html
>>>
>>>     My first attempt:
>>>
>>>     // C++
>>>       void RegisterPhysicsTypesWithLua( lua_State* lua )
>>>       {
>>>         module( lua )
>>>         [
>>>           class_<btVector3>( "btVector3" )
>>>           .def( "getX",&btVector3::getX )
>>>           .def( "getY",&btVector3::getY )
>>>           .def( "getZ",&btVector3::getZ )
>>>           .def( "setX",&btVector3::setX )
>>>           .def( "setY",&btVector3::setY )
>>>           .def( "setZ",&btVector3::setZ )
>>>         ];
>>>       }
>>>
>>>     --Lua
>>>     print("Testing btVector3 in lua")
>>>     v = btVector3()
>>>     print("btVector3 created")
>>>
>>>     print( "x = " .. v.getX() )  -- should print x = 0.0
>>>     v.setX(99.9)
>>>     print( "x = " .. v.getX() )  -- should print x = 99.9
>>>
>>>     ------------------------------------------
>>>     This first attempt produces the error:
>>>     "Attempt to call a nil value"
>>>
>>>
>>>     So I added a constructor and tried again:
>>>
>>>     // C++
>>>       void RegisterPhysicsTypesWithLua( lua_State* lua )
>>>       {
>>>         module( lua )
>>>         [
>>>           class_<btVector3>( "btVector3" )
>>>           .def( constructor<  float, float, float>() )
>>>           .def( "getX",&btVector3::getX )
>>>           .def( "getY",&btVector3::getY )
>>>           .def( "getZ",&btVector3::getZ )
>>>           .def( "setX",&btVector3::setX )
>>>           .def( "setY",&btVector3::setY )
>>>           .def( "setZ",&btVector3::setZ )
>>>         ];
>>>       }
>>>
>>>     --Lua
>>>     print("Testing btVector3 in lua")
>>>     v = btVector3(1.0,2.0,3.0)
>>>     print("btVector3 created")
>>>
>>>     print( "x = " .. v.getX() )  -- should print x = 1.0
>>>     v.setX(99.9)
>>>     print( "x = " .. v.getX() )  -- should print x = 99.9
>>>
>>>     ------------------------------------------
>>>     This second attempt produces the error:
>>>     "No such operator defined"
>>>
>>>
>>>     I have double checked that I am definately calling the
>>>     RegisterPhysicsTypesWithLua with the correct LuaState.
>>>
>>>     I expected this to be reasonably trivial as I have been exposing
>>>     my own
>>>     classes with ease. This is however, the first time I have tried to
>>>     expose a 3rd party class. Am I missing something obvious?
>>>
>>>     Thanks very much
>>>
>>>     Simon
>>>
>> Well spotted (too used to Python!). The second version works!
>>
>> However doesn't explain why the first version (with default ctor) 
>> fails. It never gets to the getX() call:
>> Testing btVector3 in lua
>> Error: Attempt to call a nil value
>>
>>
>> btVector3 does indeed have a default ctor:
>> http://www.bulletphysics.com/Bullet/BulletFull/classbtVector3.html#a82b4c5da54ecd4c91bd9b056dea0d288
>>
>> Thanks
>>
>
Thanks Tony, Didn't know I could do that.

Is this a top-posting list then? ;)

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