How do I construct a std::string from a DWORD?

Question

I have following code:

Tools::Logger.Log(string(GetLastError()), Error);

GetLastError() returns a DWORD a numeric value, but the constructor of std::string doesn't accept a DWORD.

What can I do?

Answer 1

You want to read up on ostringstream:

#include <sstream>
#include <string>

int main()
{
   std::ostringstream stream;
   int i = 5;
   stream << i;
   std::string str = stream.str();
} 

Answer 2

You want to convert the number to a string:

std::ostringstream os;
os << GetLastError();
Log(os.str(), Error);

Or boost::lexical_cast:

Log(boost::lexical_cast<std::string>(GetLastError()), Error);

Answer 3

Since C++11

std::to_string() with overloads for int, long, long long, unsigned int, unsigned long, unsigned long long, float, double, and long double.

auto i = 1337;
auto si = std::to_string(i); // "1337"
auto f = .1234f;
auto sf = std::to_string(f); // "0.123400"

Yes, I'm a fan of auto.

To use your example:

Tools::Logger.Log(std::to_string(GetLastError()), Error);

Answer 4

Use Boost's lexical_cast for simple cases such as the above:

Tools::Logger.Log(lexical_cast<string>(GetLastError()), Error);

Answer 5

You can use STLSoft's winstl::int_to_string(), as follows:

Tools::Logger.Log(winstl::int_to_string(GetLastError()), Error);

Also, if you want to lookup the string form of the error code, you can use STLSoft's winstl::error_desc.

There were a bunch of articles in Dr Dobb's about this a few years ago: parts one, two, three, four. Goes into the subject in great detail, particularly about performance.

Answer 6

Use std::stringstream.

std::stringstream errorStream;
errorStream << GetLastError();
Tools::Logger.Log(errorStream.str(), Error);

Answer 7

what i normally do is:

std::ostringstream oss;
oss << GetLastError() << " :: " << Error << std::endl;
Tools::Logger.Log(oss.str()); // or whatever interface is for logging

Answer 8

As all guys here suggested, implementation will use stringstream.
In my current project we created function

template <typename T>
std::string util::str::build( const T& value );

to create string from any source.

So in our project it would be

Tools::Logger.Log( util::str::build(GetLastError()) );

Such usage of streams in the suggested way wouldn't pass my review unless someone wrap it.