How to check whether an OptiX variable is initialized or not?

In OptiX/CUDA programs (*.cu), simple type variables can always be initialized by putting an assignment operator immediately after rtDeclareVariable:

// in CUDA program
rtDeclareVariable(int, an_integer, , ) = 0;
rtDeclareVariable(float, a_float, , ) = 0.0f;
rtDeclareVariable(float3, a_vector, , ) = { 1.0f, 0.0f, 0.0f };

But for complex type variables, such as TextureSampler and Buffer, the only way to initialize them is to set the variables in host (CPU) programs. To prevent OptiX from recompiling, make sure you initialize your OptiX variables only at the beginning and only ONCE. So to do this, you can use Variable::getType() to check if an OptiX variable is initialized:

// in CUDA program
rtBuffer<float, 1>  a_buffer;
rtTextureSampler<float4, 2> a_texture;

// in host program
Variable buf_var = context["a_buffer"];
if (buf_var->getType() == RT_OBJECTTYPE_UNKNOWN)
{
    // initialize buf_var...
    Buffer buf = context->createBuffer(...);
    buf_var->setBuffer(buf);
}
Variable tex_var = context["a_texture"];
if (tex_var->getType() == RT_OBJECTTYPE_UNKNOWN)
{
    // initialize tex_var...
    TextureSampler sampler = context->createTextureSampler(...);
    tex_var->setTextureSampler(sampler);
}

// now you can dereference the variables safely
Buffer buf = context["a_buffer"]->getBuffer();
TextureSampler tex = context["a_tex"]->getTextureSampler();