WxWidgets FAQ Helper classes
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wxWidgets consists of a large group of helper classes, that help programmers to do their job. These include classes for working with strings, files, xml files, streams, database or network. Here we will show only a tiny drop of the whole lake.
wxWidgets library can be used to create console and gui applications. In this chapter, we will illustrate some of the helper classes in console based applications.
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Console
This is a simple console application. The application puts some text into the console window.
#include <wx/string.h> int main(int argc, char **argv) { wxPuts(wxT("A wxWidgets console application")); }
A wxWidgets console application
wxString
This is probably the most useful class. wxString is a class representing a character string.
In the following example, we define three wxStrings. We create one string of these strings using addition operation.
#include <wx/string.h> int main(int argc, char **argv) { wxString str1 = wxT("Linux"); wxString str2 = wxT("Operating"); wxString str3 = wxT("System"); wxString str = str1 + wxT(" ") + str2 + wxT(" ") + str3; wxPuts(str); }
Linux Operating System
The Printf() method is used to format strings.
#include <wx/string.h> int main(int argc, char **argv) { int flowers = 21; wxString str; str.Printf(wxT("There are %d red roses."), flowers); wxPuts(str); }
There are 21 red roses.The following example checks, whether a string contains another string. For this we have a Contains() method.
#include <wx/string.h> int main(int argc, char **argv) { wxString str = wxT("The history of my life"); if (str.Contains(wxT("history"))) { wxPuts(wxT("Contains!")); } if (!str.Contains(wxT("plain"))) { wxPuts(wxT("Does not contain!")); } }
Contains! Does not contain!
The Len() method returns the number of characters in the string.
#include <wx/string.h> int main(int argc, char **argv) { wxString str = wxT("The history of my life"); wxPrintf(wxT("The string has %d characters\n"), str.Len()); }
The string has 22 charactersThe MakeLower() and MakeUpper() methods make characters lower case and upper case.
#include <wx/string.h> int main(int argc, char **argv) { wxString str = wxT("The history of my life"); wxPuts(str.MakeLower()); wxPuts(str.MakeUpper()); }
the history of my life THE HISTORY OF MY LIFE
Utility functions
wxWidgets has several handy utility functions for executing a process, getting a home user directory or getting the OS name.
In the following example, we execute the ls command. For this, we have the wxShell() function. Unix only.
#include <wx/string.h> #include <wx/utils.h> int main(int argc, char **argv) { wxShell(wxT("ls -l")); }
total 40 -rwxr-xr-x 1 vronskij vronskij 9028 2007-09-06 22:10 basic -rw-r--r-- 1 vronskij vronskij 95 2007-09-06 22:09 basic.cpp -rw-r--r-- 1 vronskij vronskij 430 2007-09-06 00:07 basic.cpp~ -rwxr-xr-x 1 vronskij vronskij 11080 2007-09-05 23:17 console -rw-r--r-- 1 vronskij vronskij 500 2007-09-05 23:17 console.cpp -rw-r--r-- 1 vronskij vronskij 485 2007-09-05 23:16 console.cpp~
Next we will we will get the home user directory, os name, user name, host name and total free memory.
#include <wx/string.h> #include <wx/utils.h> int main(int argc, char **argv) { wxPuts(wxGetHomeDir()); wxPuts(wxGetOsDescription()); wxPuts(wxGetUserName()); wxPuts(wxGetFullHostName()); long mem = wxGetFreeMemory().ToLong(); wxPrintf(wxT("Memory: %ld\n"), mem); }
/home/vronskij Linux 2.6.20-16-generic i686 jan bodnar spartan Memory: 741244928
Time & date
In wxWidgets, we have several classes for working with date & time.
The example shows current date or time in various formats.
#include <wx/datetime.h> int main(int argc, char **argv) { wxDateTime now = wxDateTime::Now(); wxString date1 = now.Format(); wxString date2 = now.Format(wxT("%X")); wxString date3 = now.Format(wxT("%x")); wxPuts(date1); wxPuts(date2); wxPuts(date3); }
Fri Sep 7 21:28:38 2007 21:28:38 09/07/07
Next we will show current time in different cities.
#include <wx/datetime.h> int main(int argc, char **argv) { wxDateTime now = wxDateTime::Now(); wxPrintf(wxT(" Tokyo: %s\n"), now.Format(wxT("%a %T"), wxDateTime::GMT9).c_str()); wxPrintf(wxT(" Moscow: %s\n"), now.Format(wxT("%a %T"), wxDateTime::MSD).c_str()); wxPrintf(wxT("Budapest: %s\n"), now.Format(wxT("%a %T"), wxDateTime::CEST).c_str()); wxPrintf(wxT(" London: %s\n"), now.Format(wxT("%a %T"), wxDateTime::WEST).c_str()); wxPrintf(wxT("New York: %s\n"), now.Format(wxT("%a %T"), wxDateTime::EDT).c_str()); }
Tokyo: Sat 05:42:24 Moscow: Sat 00:42:24 Budapest: Fri 22:42:24 London: Fri 22:42:24 New York: Fri 16:42:24
The following example shows, how we can add date spans to our date/time. We add one month to the current time.
#include <wx/datetime.h> int main(int argc, char **argv) { wxDateTime now = wxDateTime::Now(); wxString date1 = now.Format(wxT("%B %d %Y")); wxPuts(date1); wxDateSpan span(0, 1); wxDateTime then = now.Add(span); wxString date2 = then.Format(wxT("%B %d %Y")); wxPuts(date2); }
September 07 2007 October 07 2007
Files
wxWidgets has several classes to facilitate working with files. This is low level access to files, as opposed to working with streams.
In the following example, we use the wxFile class to create a new file and write data to it. We also test, whether the file is opened. Note, that when we create a file, it automatically stays as opened.
#include <wx/file.h> int main(int argc, char **argv) { wxString str = wxT("You make me want to be a better man.\n"); wxFile file; file.Create(wxT("quote"), true); if (file.IsOpened()) wxPuts(wxT("the file is opened")); file.Write(str); file.Close(); if (!file.IsOpened()) wxPuts(wxT("the file is not opened")); }
$ ls qoute ls: qoute: No such file or directory $ ./createfile the file is opened the file is not opened $ cat quote You make me want to be a better man.
The wxTextFile is a simple class which allows to work with text files on line by line basis. It is easier to work with this class than with wxFile class.
In the next example, we will print the number of lines in a file, first and last lines and finally we will read and show the contents of the file.
#include <wx/textfile.h> int main(int argc, char **argv) { wxTextFile file(wxT("test.c")); file.Open(); wxPrintf(wxT("Number of lines: %d\n"), file.GetLineCount()); wxPrintf(wxT("First line: %s\n"), file.GetFirstLine().c_str()); wxPrintf(wxT("Last line: %s\n"), file.GetLastLine().c_str()); wxPuts(wxT("-------------------------------------")); wxString s; for ( s = file.GetFirstLine(); !file.Eof(); s = file.GetNextLine() ) { wxPuts(s); } file.Close(); }
Number of lines: 8 First line: #include <glib.h> Last line: } ------------------------------------- #include <glib.h> #include <glib/gstdio.h> int main() { g_mkdir("/home/vronskij/test", S_IRWXU); }
The wxDir class allows us to enumerate files and directories.
In the following example, we will print all files and directories available in the current working directory.
#include <wx/dir.h> #include <wx/filefn.h> int main(int argc, char **argv) { wxDir dir(wxGetCwd()); wxString file; bool cont = dir.GetFirst(&file, wxEmptyString, wxDIR_FILES | wxDIR_DIRS); while (cont) { wxPuts(file); cont = dir.GetNext(&file); } }
$ ./dir dir temp console basic.cpp basic quote createfile console.cpp basic.cpp~ test.c console.cpp~
