As much as I use and appreciate the Standard C++ Library, I've never liked its string template -
basic_string<>. At times, it seems the designers went out of their way to make it difficult to use.
On the other hand, I've always loved the ease of use of MFC's
CString class. It checks for NULL pointers, implicitly converts to
const TCHAR*, and has some very handy member functions (
Load, etc.) that make string programming a breeze. But of course, I don't want to use MFC anymore. In fact, I don't want to rely on any proprietary library because I want portability.
Therefore I decided to combine the best of both worlds and create:
This is a class (a template instantiation actually) that derives from from
basic_string<TCHAR>. To the
basic_string it adds the entire
CString API. You get
CString ease of use with 100%
basic_string compatibility. In short, a
CStdString object is a
basic_string that (with very few exceptions (noted below) it is also a drop-in replacement for
CString. The best part of this is that both APIs (
CString) are well known and well documented.
I originally submitted this article to another code site (which shall remain nameless ) a few years ago. I like CodeProject so much I thought I'd submit it here too. I have used this class in almost every professional project I've done over the past 4 years. It has proven to be the single most useful piece of code I've ever written. It is also extensively debugged. I hope you like it. If you ever have any problems with it, please e-mail me. I'm happy to help.
I provided a simple source application here to prove some of the
CString functions work but it's really just a token. The list of sample projects out there that use
basic_string is massive.
- Drop in Replacement for
CString (see below for exceptions)
- Two instantiations available at all times --
CStdStringA. The name
CStdString is just a
typedef of one of these two.
- Safely checks for
NULL string pointer inputs (like
CString) in all functions
- Extra constructors and assignment operators to automatically convert between wide (
wchar_t-based) and thin (
strings for you.
- Implicit conversion to
c_str(). The C++ committee doesn't like this but I sure do.
- Builds on several platforms, including Windows, Unix and Linux. Works with several implementations of the Standard C++ Library, including Dinkumware, GNU, CodeWarrior, and STLPort.
- Win32 builds give you some extra goodies like UNICODE/MBCS conversion macros (just like MFCs) as well as member functions for persisting
CStdString objects to and from DCOM
- Makes no use of any implementation details of the base class template (
- The derived template adds no member data to
basic_string and adds no virtual functions
There are a couple of issues about this code of that I should point out.
I was unable to exactly reproduce the
CString API. There are a two functions that both
basic_string; share, but implement differently. In these cases, I felt it best to make
CStdString behave like
basic_string (the base class) rather than
CString. To be specific.
CStdString::operator returns characters by value (unlike
CString which returns them by reference)
- The constructor that takes a character and a count takes them in the order (
value) which is the opposite of the order
CString declares them. That's the order that
basic_string<>; needs and it was impossible to implement both versions.
There were also two
CString functions I could not implement at all --
Deriving From basic_string<>
The template I wrote derives from
basic_string, a class template without a virtual destructor. Any introductory text to C++ will tell you that it is dangerous to derive from a class without a virtual destructor. It can lead to behavior that is undefined. So if you were to code the following (deleting a
CStdStringA through a pointer to the base class), you would technically get undefined behavior:
std::string* pstr = new CStdStringA("Hi");
Personally, I don't think this is much of an issue. I mean really how often do you actually do this with
string objects? I have rarely (if ever) needed to dynamically allocate a
string object on the heap. And if I ever do, I won't using a base-class pointer. So if you don't do this, you'll never have to worry. In fact, even if you do code this way, I doubt you'll have any problems with
CStdString. I can tell you that at least with Microsoft Visual C++, even the above code runs just fine with no errors or memory leaks. I doubt many other compilers would give you problems either. However my doubt does not impose reality on the C++ world. Caveat Emptor.
- 7 Dec 2011: Updated source code.