Header functions - c++

Question

EDIT: by not working I mean that in my main array mA in main doesn't show any change to the elements within the array.
I have been checking my functions as I develop the headers and they have been working perfectly: Until I got to the final header MonitorArray.h.
mA.getScreen(i).checkScreen();
Didn't work and I couldn't work out why. So I created a new function within MonitorArray to do a similar job using the same function, and to my surprise it worked.
mA.pollScreens();
Which uses (Inside MonitorArray.h):
monitorArray[i].checkScreen();
Function getScreen:
ScreenArray MonitorArray::getScreen(int arrayPointer)
{
if (arrayPointer<0 || arrayPointer>=monitors)
{
return false;
}
else
{
return monitorArray[arrayPointer];
}
}
Function checkScreen and addArray:
void ScreenArray::checkScreen()
{
HDC dMonitor;
PixelArray pArray;
int lenX = 0, lenY = 0;
dMonitor = CreateDC(iMonitor.szDevice, iMonitor.szDevice, NULL, NULL);
lenX = (iMonitor.rcWork.right - iMonitor.rcWork.left) - 1;
lenY = (iMonitor.rcWork.bottom - iMonitor.rcWork.top) - 1;
pArray.setColour(0, GetPixel(dMonitor, 0, 0));
pArray...
...
...
addArray(&pArray);
ReleaseDC(NULL, dMonitor);
}
void ScreenArray::addArray(PixelArray* pA)
{
if (previousCheck(*pA))
{
arrayPosition = 0;
screenArray[arrayPosition] = *pA;
arrayPosition++;
}
else
{
screenArray[arrayPosition] = *pA;
arrayPosition++;
}
if (arrayPosition==11)
{
//Run screen saver on monitor
}
}
Why does running the command within the header file through a new function work but running the functions from main not?

Answer 1

Assuming that "didn't work" means "didn't affect the ScreenArray in my MonitorArray", it's because getScreen returns a copy of the array element
ScreenArray MonitorArray::getScreen(int arrayPointer)
while the new member function most likely works with the array directly.
You'll need to return a pointer to the array element instead:
ScreenArray* MonitorArray::getScreen(int arrayPointer)
{
if (arrayPointer<0 || arrayPointer>=monitors)
{
return NULL;
}
else
{
return &monitorArray[arrayPointer];
}
}
(BTW: the implicit conversion from bool to ScreenArray looks very odd.)