CODEWITHSUNDEEP
c++11concatenationwchar-tbstr-t
Nikola
Nikola

Reputation: 29

How to concatenate string in _bstr_t and wchar_t?

I have _bstr_t string and I have wchar_t and one unsigned int variables which I want to put to the string...

_bstr_t strCnn("Driver={SQL Server};Server=some_host,some_port;Database=some_db;User ID=some_user;Password=some_psw;");

wchar_t *host,
unsigned int port,
wchar_t *db_name,
wchar_t *user,
wchar_t *password,

These 5 variables I pass to the function which does connection. Can you please guide me how to insert them to connection string.

I tried this way:

    wstring ws(host);
    string host_str(ws.begin(), ws.end());
    wstring ws_db(db_name);
    string db_str(ws_db.begin(), ws_db.end());
    wstring ws_user(user);
    string user_str(ws_user.begin(), ws_user.end());
    wstring ws_psw(password);
    string psw_str(ws_psw.begin(), ws_psw.end());

    std::string port_str = std::to_string(port);
    _bstr_t strCnn("Driver={SQL Server};Server="+host_str+","+port_str+";Database="+db_str+";User ID="+user_str+";Password="+psw_str+";");

But it says:

Error E0289 no instance of constructor "_bstr_t::_bstr_t" matches the argument list 
Error C2664 '_bstr_t::_bstr_t(const _bstr_t &) throw()': cannot convert argument 1 from 'std::basic_string<char,std::char_traits<char>,std::allocator<char>>' to 'const char *'

Upvotes: 1

Views: 345

Answers (2)

1201ProgramAlarm
1201ProgramAlarm

Reputation: 32742

When you construct the string to pass to strCnn, it is a std::string object. _bstr_t does not have a constructor that takes a string, but does have one that takes const char * (which is what the error message is telling you.

The simple fix is to construct your string and save that in a local variable, then pass that string (converted to a const char *) to the _bstr_t constructor.

std::string port_str = std::to_string(port);
std::string connection = "Driver={SQL Server};Server="+host_str+","+port_str+";Database="+db_str+";User ID="+user_str+";Password="+psw_str+";";
_bstr_t strCnn(connection.c_str());

This may not be the optimal way to construct a string (std::stringstream may be better).

Since your original parameter strings are wide characters, you can construct the connection string with wide characters (and std::wstring).

Upvotes: 1

Leśny Rumcajs
Leśny Rumcajs

Reputation: 2516

Perhaps the easiest way would be to use std::wstringstream.

Your code could then look something like:

    std::wstringstream ws;
    ws << "Driver={SQL Server};Server=" << host << "," << port << ";Database=" << db << ";User ID=" << user << ";Password=" << pswr <<";";
    _bstr_t strCnn(ws.str().c_str());

The constructor of _bstr_t takes a const wchar_t* so no need to do any intermediary conversions.

Upvotes: 1

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