Converting a std::wstring to int

Question

I presume this to be very simple but I cannot get it to work.

I am simply trying to convert a std::wstring to an int.

I have tried two methods so far.

The first is to use the "C" method with atoi like so:

int ConvertedInteger = atoi(OrigWString.c_str());

However, VC++ 2013 tells me:

Error, argument of type const wchar_t * is incompatible with parameter of type const char_t *

So my second method was to use this, per Google search:

std::wistringstream win(L"10"); int ConvertedInteger; if (win >> ConvertedInteger && win.eof()) { // The eof ensures all stream was processed and // prevents acccepting "10abc" as valid ints. }

However VC++ 2013 tells me this:

Error: incomplete type not allowed.

What am I doing wrong here?

Is there a better way to convert a std::wstring to int and back?

Did you #include <sstream>? Your code with the stringstream should work. — Praetorian
– Praetorian, Commented Apr 19, 2014 at 2:55
Please try to convert string using int ConvertedInteger = _wtoi(OrigWString);... — A B
– A B, Commented Apr 19, 2014 at 4:30
You could always construct a std::string from the string and use std::stoi on that. You might incur a memory allocation if the number is big enough, but I doubt it's any worse than using stringstreams. — Stuart Olsen
– Stuart Olsen, Commented Apr 19, 2014 at 4:41
also I think #include <istream> is required for wistringstream — M.M
– M.M, Commented Apr 19, 2014 at 5:39

Azeem · Accepted Answer · 2018-03-22 08:03:38Z

No need to revert to C api (atoi), or non portable API (_wtoi), or complex solution (wstringstream) because there are already simple, standard APIs to do this kind of conversion : std::stoi and std::to_wstring.

#include <string> std::wstring ws = L"456"; int i = std::stoi(ws); // convert to int std::wstring ws2 = std::to_wstring(i); // and back to wstring

One reason to avoid using sto*() functions family is because they all throw exceptions. ato*() don't

A B · Accepted Answer · 2014-04-19 16:02:50Z

-1

you can use available API from wstring.h.

to convert WString to int try int ConvertedInteger = _wtoi(OrigWString);.

for reference use msdn.microsoft.com/en-us/library/aa273408(v=vs.60).aspx.

edited Apr 19, 2014 at 16:02

answered Apr 19, 2014 at 4:35

A B

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3 Comments

Praetorian Over a year ago

What do you mean by stream returns the string values? The OP's code works, the error is elsewhere.

A B Over a year ago

@Praetorian I mean that when we write/ read data to/ from stream object it works on string values in OP case it is wstring

Praetorian Over a year ago

The OP is using wistringstream which deals with wchar_ts, not chars. Once again, his code works, look at the link in my previous comment. The error message about using an incomplete type most likely means he forgot to include some header file.

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