Compiler cannot convert the arguments passed to swprintf function, winapi - visual-studio-2010

Question

can you help me with this code? I cannot fix it. There is problem with swprintf function.
LRESULT CALLBACK DlgProc(HWND hWndDlg, UINT Msg, WPARAM wParam, LPARAM lParam)
{
LPTSTR strPrincipal = new TCHAR[20],
strInterest = new TCHAR[20], strPeriods = new TCHAR[20],
strInterestEarned = new TCHAR[20], strAmountEarned = new TCHAR[20];
double Principal, AnnualRate, InterestEarned;
double FutureValue, RatePerPeriod;
int NumberOfPeriods, CompoundType;
double i;
int n;
swprintf(strInterestEarned, "$%.2f", InterestEarned);
swprintf(strAmountEarned, "$%.2f", FutureValue);
}
Here are errors:
Error 1 error C2665: 'swprintf' : none of the 2 overloads could convert all the argument types
Error 2 error C2665: 'swprintf' : none of the 2 overloads could convert all the argument types

Answer 1

I think you've got your parameters wrong / in the wrong order. Have you checked the MSDN page?
Method signature:
int swprintf(
wchar_t *buffer,
size_t count,
const wchar_t *format [,
argument]...
);
That page gives the following example for swprintf:
// crt_swprintf.c
// wide character example
// also demonstrates swprintf returning error code
#include <stdio.h>
int main( void )
{
wchar_t buf[100];
int len = swprintf( buf, 100, L"%s", L"Hello world" );
printf( "wrote %d characters\n", len );
len = swprintf( buf, 100, L"%s", L"Hello\xffff world" );
// swprintf fails because string contains WEOF (\xffff)
printf( "wrote %d characters\n", len );
}
I think you'd want something along the lines of:
swprintf( strInterestEarned, 20, L"%.2f", InterestEarned );