C++ Instantiation - c++

Question

I have Vector class, representing a 3D point, written as follows in Vector.h:
class Vector {
public:
float x,y,z;
Vector(float _x=0.0,float _y=0.0,float _z=0.0){x=_x;y=_y;z=_z;};
operator float *() { return &x;};
};
I also declare a extern vector<Vector>model_vertices; on model.h
On a model.cpp file I implement Vector.h and declare a std::vector<Vector>model_vertices; globally (yes, I know the vector/Vector thing is confusing, but I must use the Vector naming for consistency).
On model.cpp, when initializing the contents of this vector I use a for loop with the following content:
float X,Y,Z;
offFileStream>>X;
offFileStream>>Y;
offFileStream>>Z;
Vector v=new Vector(X,Y,Z);
model_vertices[loadVertexIndex]=v;
I get the following error:
error C2440: 'initializing' : cannot convert from 'Vector *' to 'Vector'
Why?

Answer 1

The error is on this line:
Vector v=new Vector(X,Y,Z);
v is of type Vector, but new Vector(X,Y,Z) returns a Vector*:
What you probably wanted instead is just:
Vector v(X,Y,Z);
As a side note, I didn't see you initialize a size for the model_vertices. So you may want to use push_back() instead.

Answer 2

It's not quite clear what you're trying to achieve, but perhaps you're overthinking this.
First off, please forget the keyword new. Just pretend it doesn't exist. (By the time you'll need it, you'll know enough C++ to realize that you can ignore this post.)
Second, you can improve your class constructor to use an initializer list:
Vector(float _x = 0.0, float _y = 0.0, float _z = 0.0)
: x(_x), y(_y), z(_z)
{ }
Third, to populate a vector, just insert temporaries directly:
std::vector<Vector> v;
float x, y, z;
while (get_values(x,y,z)) // or any sort of loop you like
{
v.push_back(Vector(x,y,z));
}
If you have a recent version of C++, you can use the more efficient emplacement instead:
v.emplace_back(x, y, z); // no temporary

Answer 3

Vector v=new Vector(X,Y,Z);
model_vertices[loadVertexIndex]=v;
should be
Vector *v=new Vector(X,Y,Z);
model_vertices[loadVertexIndex]=*v;
new() allocated from the heap and it returns a pointer to an object.
If you want to call the constructor and allocate on the stack, do this instead.
Vector v(X,Y,Z);

Answer 4

The new operator can only be used when asigning to a pointer. If you just want to have an object v of type vector then you should use:
Vector v(X,Y,Z);
If you would like to have a pointer to Vector object then you should use:
Vector *v=new Vector(X,Y,Z);