I'm trying to overload the Insertion Operator. One method works, the other does not - but I'm not sure why, as they seem identical to me. Here's the relevant code (irrelevant sections chopped out):
#include <string>
#include <fstream>
#define UINT unsigned int
///////////////////////////////////////////////////////////
class Date
{
public:
// These just return unsigned ints
UINT Month();
UINT Day();
UINT Year();
UINT month;
UINT day;
UINT year;
};
///////////////////////////////////////////////////////////
class BinaryFileWriter
{
public:
virtual bool Open(string i_Filename);
void Write(UINT i_Uint);
private:
ofstream ofs;
};
template <typename T1>
BinaryFileWriter& operator << (BinaryFileWriter& i_Writer, T1& i_Value)
{
i_Writer.Write(i_Value);
return(i_Writer);
}
bool BinaryFileWriter::Open(string i_Filename)
{
ofs.open(i_Filename, ios_base::binary);
}
void BinaryFileWriter::Write(UINT i_Uint)
{
ofs.write(reinterpret_cast<const char*>(&i_Uint), sizeof(UINT));
}
///////////////////////////////////////////////////////////
void Some_Function(Date i_Game_Date)
{
BinaryFileWriter bfw;
bfw.Open("test1.txt");
// This works
UINT month = i_Game_Date.Month();
UINT day = i_Game_Date.Day();
UINT year = i_Game_Date.Year();
bfw << month << day << year;
// This does not - gives me error 'error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'unsigned int' (or there is no acceptable conversion) '
bfw << (m_Game_Date.Month()) << (m_Game_Date.Day()) << (m_Game_Date.Year());
So why does the first output line (where I get the UINT values first, berfore outputting) compile just fine, but not the second (where I use the return values of the date methods as input to my overloaded insertion operator)?
In the first line, you are able use month
, day
, and year
can be converted to INT&
.
In the second line, you are using the return values of the member functions. They are temporary objects. They cannot be bound to INT&
.
In order to be able to use,
bfw << (m_Game_Date.Month()) << (m_Game_Date.Day()) << (m_Game_Date.Year());
The second argument of the operator<<
function must be a T1 const&
, not T1&
.
template <typename T1>
BinaryFileWriter& operator << (BinaryFileWriter& i_Writer, T1 const& i_Value)
{
i_Writer.Write(i_Value);
return(i_Writer);
}
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