@li @ref overview_string_comparison
@li @ref overview_string_advice
@li @ref overview_string_related
-@li @ref overview_string_refcount
@li @ref overview_string_tuning
@section overview_string_intro Introduction
-wxString is a class which represents a character string of arbitrary length
-(limited by @c MAX_INT which is usually 2147483647 on 32 bit machines) and
+wxString is a class which represents a character string of arbitrary length and
containing arbitrary characters. The ASCII NUL character is allowed, but be
aware that in the current string implementation some methods might not work
correctly in this case.
-wxString works with both ASCII (traditional, 7 or 8 bit, characters) as well as
-Unicode (wide characters) strings.
+Since wxWidgets 3.0 wxString internally uses UCS-2 (basically 2-byte per
+character wchar_t) under Windows and UTF-8 under Unix, Linux and
+OS X to store its content. Much work has been done to make
+existing code using ANSI string literals work as before.
This class has all the standard operations you can expect to find in a string
class: dynamic memory management (string extends to accommodate new
-characters), construction from other strings, C strings and characters,
-assignment operators, access to individual characters, string concatenation and
-comparison, substring extraction, case conversion, trimming and padding (with
+characters), construction from other strings, C strings, wide character C strings
+and characters, assignment operators, access to individual characters, string
+concatenation and comparison, substring extraction, case conversion, trimming and padding (with
spaces), searching and replacing and both C-like @c printf (wxString::Printf)
and stream-like insertion functions as well as much more - see wxString for a
list of all functions.
to buffer overflows. At last, C++ has a standard string class (std::string). So
why the need for wxString? There are several advantages:
-@li <b>Efficiency:</b> This class was made to be as efficient as possible: both in
- terms of size (each wxString objects takes exactly the same space as a
- <tt>char*</tt> pointer, see @ref overview_string_refcount
- "reference counting") and speed. It also provides performance
- @ref overview_string_tuning "statistics gathering code" which may be
- enabled to fine tune the memory allocation strategy for your particular
- application - and the gain might be quite big.
+@li <b>Efficiency:</b> Since wxWidgets 3.0 wxString uses std::string (UTF8
+ mode under Linux, Unix and OS X) or std::wstring (MSW) internally by
+ default to store its constent. wxString will therefore inherit the
+ performance characteristics from std::string.
@li <b>Compatibility:</b> This class tries to combine almost full compatibility
with the old wxWidgets 1.xx wxString class, some reminiscence to MFC
CString class and 90% of the functionality of std::string class.
wxString::Printf. Of course, all the standard string operations are
supported as well.
@li <b>Unicode wxString is Unicode friendly:</b> it allows to easily convert to
- and from ANSI and Unicode strings in any build mode (see the
- @ref overview_unicode "unicode overview" for more details) and maps to
- either @c string or @c wstring transparently depending on the current mode.
+ and from ANSI and Unicode strings (see the @ref overview_unicode "unicode overview"
+ for more details) and maps to @c wstring transparently.
@li <b>Used by wxWidgets:</b> And, of course, this class is used everywhere
inside wxWidgets so there is no performance loss which would result from
conversions of objects of any other string class (including std::string) to
However, there are several problems as well. The most important one is probably
that there are often several functions to do exactly the same thing: for
-example, to get the length of the string either one of @c length(),
+example, to get the length of the string either one of wxString::length(),
wxString::Len() or wxString::Length() may be used. The first function, as
almost all the other functions in lowercase, is std::string compatible. The
second one is the "native" wxString version and the last one is the wxWidgets
This leads us to the following general advice: all functions taking string
arguments should take <tt>const wxString</tt> (this makes assignment to the
-strings inside the function faster because of
-@ref overview_string_refcount "reference counting") and all functions returning
-strings should return wxString - this makes it safe to return local variables.
+strings inside the function faster) and all functions returning strings
+should return wxString - this makes it safe to return local variables.
@section overview_string_related String Related Functions and Classes
wxStrings.
-@section overview_string_refcount Reference Counting and Why You Shouldn't Care
-
-All considerations for wxObject-derived
-@ref overview_refcount "reference counted" objects are valid also for wxString,
-even if it does not derive from wxObject.
-
-Probably the unique case when you might want to think about reference counting
-is when a string character is taken from a string which is not a constant (or
-a constant reference). In this case, due to C++ rules, the "read-only"
-@c operator[] (which is the same as wxString::GetChar()) cannot be chosen and
-the "read/write" @c operator[] (the same as wxString::GetWritableChar()) is
-used instead. As the call to this operator may modify the string, its data is
-unshared (COW is done) and so if the string was really shared there is some
-performance loss (both in terms of speed and memory consumption). In the rare
-cases when this may be important, you might prefer using wxString::GetChar()
-instead of the array subscript operator for this reasons. Please note that
-wxString::at() method has the same problem as the subscript operator in this
-situation and so using it is not really better. Also note that if all string
-arguments to your functions are passed as <tt>const wxString</tt> (see the
-@ref overview_string_advice section) this situation will almost never arise
-because for constant references the correct operator is called automatically.
-
-
@section overview_string_tuning Tuning wxString for Your Application
@note This section is strictly about performance issues and is absolutely not
necessary to read for using wxString class. Please skip it unless you feel
-familiar with profilers and relative tools. If you do read it, please also
-read the preceding section about
-@ref overview_string_refcount "reference counting".
+familiar with profilers and relative tools.
For the performance reasons wxString doesn't allocate exactly the amount of
memory needed for each string. Instead, it adds a small amount of space to each
// delete all vowels from the string
wxString DeleteAllVowels(const wxString& original)
{
+ wxString vowels( "aeuioAEIOU" );
wxString result;
-
- size_t len = original.length();
- for ( size_t n = 0; n < len; n++ )
+ wxString::const_iterator i;
+ for ( i = original.begin(); i != original.end(); ++i )
{
- if ( strchr("aeuio", tolower(original[n])) == NULL )
- result += original[n];
+ if (vowels.Find( *i ) == wxNOT_FOUND)
+ result += *i;
}
return result;
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