Expression must have pointer-to-class-type
it
is an iterator to a pointer to a MachineState
.
You need to dereference the iterator and then the pointer.
Point points[3] = {(*it)->point1, (*it)->point2, (*it)->point3};
Edit:
Dereferencing means getting the thing that it's referring to.
Dereferencing is done with the *
or ->
operator.
If it
were a MachineState
, you could use it.point1
If it
were a pointer to a MachineState
, you could use it->point1
or (*it).point1
If it
were a iterator to a MachineState
, you could also use it->point1
or (*it).point1
Since it
is an iterator to a pointer to a MachineState
, you must use (*it)->point1
or (**it).point1
John Kemp
Updated on November 28, 2020Comments
-
John Kemp over 3 years
I have a struct "MachineState" and i created a list of type "MachineState*". When i Try to iterate through the list i Keep getting "
error C2839: invalid return type 'MachineState **' for overloaded 'operator ->
I'm using Microsoft Visual Studio 10. I googled the error and all i could find out was "The -> operator must return a class, struct, or union, or a reference to one."
Struct MachineState { template <typename MachineTraits> friend class Machine; enum Facing { UP, RIGHT, DOWN, LEFT}; MachineState() : m_ProgramCounter(1) , m_ActionsTaken(0) , m_Facing(UP) , m_Test(false) , m_Memory(nullptr) ,x(0) ,y(0) ,point1(25, 10) ,point2(10, 40) ,point3(40, 40) { } int m_ProgramCounter; int m_ActionsTaken; Facing m_Facing; bool m_Test; int x; int y; Point point1; Point point2; Point point3; };
I declare the list as
std::list<MachineState*> zombs;
Here is where I try to iterate through my list and i keep getting the error, on the "it->point1" saying that the expression must have a pointer to class type.
for(std::list<MachineState*>::iterator it = zombs.begin(); it != zombs.end(); it++) { Point points[3] = {it->point1, it->point2, it->point3}; Point* pPoints = points; SolidBrush brush(Color(255, 255, 0, 0)); m_GraphicsImage.FillPolygon(&brush, pPoints,3); }
If anyone can explain me what's wron