Converting everything to and from wxString

This question seems common so I thought I'd write an article. Note that sometimes there may be more than one possible solutions, so don't forget to check the docs.

Note that it is recommended to use wxString as much as possible. Do no use char* or std::string unless you use a third-party library that requires you to do so.

Literals

A literal is a string written in code with "quotes around it". A literal is not a wxString, and (in wxWidgets 2.8) will not be implicitly converted to one. This means that you can never pass in a raw literal into a wxWidget function or method (unless you don't care about your app not building with Unicode-enabled wxWidgets builds)

MessageBox("I'm a mistake!")  // WRONG in WxWidgets 2.8 (OK in 2.9)

Instead, wxWidgets (prior to wxWidgets 2.9) requires you to use one of these macros to turn literals into wxString-compatible characters:

_("text that can be translated")
wxT("text that won't be translated")
_T("same as wxT")

char* c = "sometext";
wxT(c) // WRONG, not a literal

Rather than being a nuisance, the _(), wxT(), and _T() macros take care of some unicode issues and help with internationalization.

char* to wxString

char* chars = "Hello world";
// assuming your string is encoded as UTF-8, change the wxConv* parameter as needed
wxString mystring(chars, wxConvUTF8);

wxString to char*

void my_function(const char* foo)
{
}
...
wxString mystring(wxT("HelloWorld"));
// you could give the encoding you want as a parameter to mb_str(), e.g. mb_str(wxConvUTF8)
my_function( mystring.mb_str() );

mb_str() returns a temporary pointer. If you need to store it in a char* (but why would you? ;) :

wxString mystring(wxT("HelloWorld"));
char cstring[1024];
// assuming you want UTF-8, change the wxConv* parameter as needed
strncpy(cstring, (const char*)mystring.mb_str(wxConvUTF8), 1023);

You can also use ToUTF8(), since which encoding you get is clearer than with mb_str()

wxString to TCHAR

TCHAR tCharString[255];
wxString myString(_T("Hello World"));
const wxChar* myStringChars = myString.c_str();  
for (int i = 0; i < myString.Len(); i++) {
   tCharString[i] = myStringChars [i];
}
tCharString[myString.Len()] = _T('\0');

int to wxString

wxString mystring = wxString::Format(wxT("%i"),myint);

or

wxString mystring;
mystring << myint;

float to wxString

wxString mystring = wxString::Format(wxT("%f"), myfloat);

or

wxString mystring;
mystring << myfloat;

wxString to integer number

wxString number(wxT("145"));
long value;
if(!number.ToLong(&value)) { /* error! */ }

or

wxString str = _T("123");
int num;

num = wxAtoi(str);

wxString to floating-point number

wxString number(wxT("3.14159"));
double value;
if(!number.ToDouble(&value)){ /* error! */ }

std::string to wxString

std::string stlstring = "Hello world";
// assuming your string is encoded as UTF-8, change the wxConv* parameter as needed
wxString mystring(stlstring.c_str(), wxConvUTF8);

wxString to std::string

wxWidgets 2.8 :

wxString mystring(wxT("HelloWorld"));
std::string stlstring = std::string(mystring.mb_str());

Under wxWidgets 2.9, you may use

wxString::ToStdString()