Basic CString Operations
This topic explains the following basic CString operations:
Class CString is based on class template CStringT Class.
CString is a typedef of
CStringT. More exactly,
CString is a typedef of an explicit specialization of
CStringT, which is a common way to use a class template to define a class. Similarly defined classes are
CStringW are defined in atlstr.h.
CStringT is defined in cstringt.h.
CStringW each get a set of the methods and operators defined by
CStringT for use with the string data they support. Some of the methods duplicate and, in some cases, surpass the string services of the C run-time libraries.
CString is a native class. For a string class that is for use in a C++/CLI managed project, use
Creating CString Objects from Standard C Literal Strings
You can assign C-style literal strings to a
CString just as you can assign one
CString object to another.
Assign the value of a C literal string to a
CString myString = _T("This is a test");
Assign the value of one
CString oldString = _T("This is a test"); CString newString = oldString;
The contents of a
CStringobject are copied when one
CStringobject is assigned to another. Therefore, the two strings do not share a reference to the actual characters that make up the string. For more information about how to use
CStringobjects as values, see CString Semantics.
To write your application so that it can be compiled for Unicode or for ANSI, code literal strings by using the _T macro. For more information, see Unicode and Multibyte Character Set (MBCS) Support.
Accessing Individual Characters in a CString
You can access individual characters in a
CString object by using the
SetAt methods. You can also use the array element, or subscript, operator ( [ ] ) instead of
GetAt to get individual characters. (This resembles accessing array elements by index, as in standard C-style strings.) Index values for
CString characters are zero-based.
Concatenating Two CString Objects
To concatenate two
CString objects, use the concatenation operators (+ or +=), as follows.
CString s1 = _T("This "); // Cascading concatenation s1 += _T("is a "); CString s2 = _T("test"); CString message = s1 + _T("big ") + s2; // Message contains "This is a big test".
At least one argument to the concatenation operators (+ or +=) must be a
CString object, but you can use a constant character string (for example,
"big") or a char (for example, 'x') for the other argument.
Comparing CString Objects
Compare method and the == operator for
CString are equivalent.
Compare, operator==, and
CompareNoCase are MBCS and Unicode aware;
CompareNoCase is also case-insensitive. The
Collate method of
CString is locale-sensitive and is often slower than
Collate only where you must abide by the sorting rules as specified by the current locale.
The following table shows the available CString comparison functions and their equivalent Unicode/MBCS-portable functions in the C run-time library.
|CString function||MBCS function||Unicode function|
CStringT class template defines the relational operators (<, <=, >=, >, ==, and !=), which are available for use by
CString. You can compare two
CStrings by using these operators, as shown in the following example.
CString s1(_T("Tom")); CString s2(_T("Jerry")); ASSERT(s2 < s1);
Converting CString Objects
For information about converting CString objects to other string types, see How to: Convert Between Various String Types.
Using CString with wcout
To use a CString with
wcout you must explicitly cast the object to a
const wchar_t* as shown in the following example:
CString cs("meow"); wcout <<(const wchar_t*) cs <<endl;
Without the cast,
cs is treated as a
wcout prints the address of the object. This behavior is caused by subtle interactions between template argument deduction and overload resolution which are in themselves correct and conformant with the C++ standard.