来自另一个具有数组初始化功能的构造函数的C ++构造函数调用

Question

I am writing a new class using OpenGL, i have two possibilities for my constructor :

VertexObject();
VertexObject(GLuint* vertices,GLuint* elements);

What i would like to do is that VertexObject() calls the other one with an already inisialised array such as

    VertexObject::VertexObject() : 
    VertexObject( 
    (GLuint[]) {
        0, 1, 2,
        2, 3, 0
    },
    (GLuint[]) {
        0, 1, 2,
        2, 3, 0
    }) {}

But it seems C++ won't let me do it, error being 'taking address of temporary array'. I am not even sure what i am asking for is doable but any help will be greatly appreciated.

Answer 1

I propose you to look at boost library, particularly assign pattern(facilitates initialization of containers) might help.

Here is a small code snippet that might give you grasp of idea:

VertexObjectc(boost::assign::list_of(0)(1)(2)(2)(3)(0).convert_to_container<GLuint>() );

I haven`t tested it.

Answer 2

If you deep copy the array in the constructor or if the arrays are never ever modified and VertexObject doesn't take the ownership of the pointers, this should work:

GLuint def_vert[6] = { // static storage
    0, 1, 2,
    2, 3, 0
};
VertexObject::VertexObject() : 
VertexObject(def_vert, def_vert) {}

You can use separate arrays if you want different values for each parameter of course.

Answer 3

Try this:

// VertexObject.h
class VertexObject
{
private:
    static const GLuint m_default_vertices[6], m_default_elements[6];
    static GLuint *GetDefVertices();
    static GLuint *GetDefElements();
public:
    VertexObject() : VertexObject(GetDefVertices(), GetDefElements()) { }
    ...
};
// VertexObject.cpp
const GLuint VertexObject::m_default_vertices[6] = {
    0, 1, 2,
    2, 3, 0
};
const GLuint VertexObject::m_default_elements[6] = {
    0, 1, 2,
    2, 3, 0
};
GLuint *VertexObject::GetDefVertices()
{
    static thread_local GLuint ar[6];
    memcpy(ar, m_default_vertices, sizeof(ar));
    return ar;
}
GLuint *VertexObject::GetDefElements()
{
    static thread_local GLuint ar[6];
    memcpy(ar, m_default_elements, sizeof(ar));
    return ar;
}

( http://ideone.com/IvujSq )

Note that it works on C++11.