Open File Dialog Box - objective-c

Question

I'm learning Objective-C and trying to develop a simple zipper application, but I stopped when now, when I need to insert a button at my dialog and this button opens a Open File Dialog that will select a file to compress, but I never used a Open File Dialog, then how I can open it and store the user selected file in a char*? Thanks.
Remember that I'm using GNUstep(Linux).

Answer 1

Thanks #Vlad the Impala I am updating your answers for people who use OS X v10.6+
// Create the File Open Dialog class.
NSOpenPanel* openDlg = [NSOpenPanel openPanel];
// Enable the selection of files in the dialog.
[openDlg setCanChooseFiles:YES];
// Multiple files not allowed
[openDlg setAllowsMultipleSelection:NO];
// Can't select a directory
[openDlg setCanChooseDirectories:NO];
// Display the dialog. If the OK button was pressed,
// process the files.
if ( [openDlg runModal] == NSOKButton )
{
// Get an array containing the full filenames of all
// files and directories selected.
NSArray* urls = [openDlg URLs];
// Loop through all the files and process them.
for(int i = 0; i < [urls count]; i++ )
{
NSString* url = [urls objectAtIndex:i];
NSLog(#"Url: %#", url);
}
}

Answer 2

In case someone else needs this answer, here it is:
int i;
// Create the File Open Dialog class.
NSOpenPanel* openDlg = [NSOpenPanel openPanel];
// Enable the selection of files in the dialog.
[openDlg setCanChooseFiles:YES];
// Multiple files not allowed
[openDlg setAllowsMultipleSelection:NO];
// Can't select a directory
[openDlg setCanChooseDirectories:NO];
// Display the dialog. If the OK button was pressed,
// process the files.
if ( [openDlg runModalForDirectory:nil file:nil] == NSOKButton )
{
// Get an array containing the full filenames of all
// files and directories selected.
NSArray* files = [openDlg filenames];
// Loop through all the files and process them.
for( i = 0; i < [files count]; i++ )
{
NSString* fileName = [files objectAtIndex:i];
}

Answer 3

For people who use OS X v10.10+, replace in Far Jangtrakool answer:
if ( [openDlg runModal] == NSOKButton )
by
if ( [openDlg runModal] == NSModalResponseOK )