Deleting code

Created 11/23/2006, updated 6 weeks ago3 minute read

Sometimes deleting code is the best kind of enhancement you can make.

Here’s a quick example trimmed down to show only the relevant context. In this case we’re talking about replacing this:

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    // check Dock icon state: http://wincent.dev/a/support/bugs/show_bug.cgi?id=393
    BOOL wasVisibleAtLaunch = [[WODockIcon sharedIcon] isVisible];
    BOOL shouldBeVisible    = (![defaults boolForKey:WO_PREF_GENERAL_NO_ICON_IN_DOCK]);
    unless (wasVisibleAtLaunch == shouldBeVisible)
    {
        // detected a discrepancy: ask if user wants to proceed with change
        NSString *hiddenOrVisible = (shouldBeVisible ? _WO_VISIBLE : _WO_HIDDEN);
        int returnValue = NSRunAlertPanel(_WO_DOCK_ICON_NEEDS_UPDATING,         // title
                                          _WO_DOCK_ICON_UPDATE_EXPLANATION,     // message
                                          _WO_UPDATE,                           // default button
                                          _WO_DO_NOT_UPDATE,                    // alternate button
                                          nil,                                  // other button
                                          hiddenOrVisible);                     // "hidden" or "visible"
        if (returnValue == NSAlertDefaultReturn)
            [self attemptSetDockIconVisible:shouldBeVisible];
    }
}


- (void)attemptSetDockIconVisible:(BOOL)visible
{
    BOOL failed = NO;
    if ([NSApp infoDictionaryIsWriteable])              // try modifying plist
        failed = (![NSApp setDockIconVisible:visible]);
    else                                                // plist is not writeable
    {
        if ([NSApp infoDictionaryIsOnWriteableVolume])
        {
            // create temporary plist file
            int fd; // file descriptor for temporary file
            NSString *tempPlist = [[NSApp infoDictionaryWithDockIconVisible:visible] writeToTemporaryFile:&fd];


            if (tempPlist)
            {
                // try to authenticate as root
                WOSudo      *sudo       = [[WOSudo alloc] init];
                NSString    *copyTool   = @"/bin/cp";
                NSString    *plistPath  = [NSString stringWithUTF8String:[tempPlist fileSystemRepresentation]];
                NSArray     *arguments  = [NSArray arrayWithObjects:plistPath, [NSApp infoDictionaryPath], nil];
                [sudo setArgs:arguments forTool:copyTool];


                // copy temporary file over old file with root privileges
                NSString *prompt = _WO_SUDO_PROMPT;
                if ([sudo authenticateAndAuthorizeWithPrompt:prompt])
                {
                    int result = [sudo executeTool:copyTool withArgs:arguments returnImmediately:NO];
                    if (result != EXIT_SUCCESS)
                        failed = YES;
                }
                else
                    failed = YES;                   // user failed to authenticate or cancelled


                [sudo release];
                close(fd);
            }
            else
                failed = YES;                       // could not create temporary plist file
        }
        else                                        // not on writeable volume
        {
            // advise user to copy application onto a writeable volume
            (void)NSRunAlertPanel(_WO_NOT_ON_WRITABLE_VOLUME,           // title
                                  _WO_COPY_TO_WRITABLE_VOLUME,          // message
                                  _WO_OK,                               // default button
                                  nil, nil);                            // alternate and other buttons
            return;
        }
    }


    if (failed)
    {
        (void)NSRunAlertPanel(_WO_COULD_NOT_CHANGE_SETTING,             // title
                              _WO_TRY_AGAIN_LATER,                      // message
                              _WO_OK,                                   // default button
                              nil, nil);                                // alternate and other buttons
    }
    else // success: reset Launch Services database and offer to restart
    {
        [NSApp resetLaunchServicesDatabase];
        int returnValue = NSRunAlertPanel(_WO_CHANGED_SETTING,          // title
                                          _WO_RELAUNCH_TO_SEE_CHANGE,   // message
                                          _WO_RELAUNCH,                 // default button
                                          _WO_LATER,                    // alternate button
                                          nil);                         // other button
        if (returnValue == NSAlertDefaultReturn)
            [self relaunch];
    }
}

With this:

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    if (![defaults boolForKey:WO_PREF_GENERAL_NO_ICON_IN_DOCK]) // dock icon should be visible
        (void)[NSApp transformToForegroundApplication];
}

Now obviously those examples won’t compile as-is because they depend on other methods and macros which aren’t shown, but you get the idea. Not only is the new code shorter and therefore easier to maintain (and in fact, there’s other glue code for handling the preferences interface which isn’t shown above but which can also be deleted; in total we’re talking about a few hundred lines of code that can be thrown away) but it’s also better for a number of other reasons: it plays nicely with Leopard’s code signing feature, works for non-admin users even when the application is installed in a location writeable only by admins, works even when the application is running from a non-writeable volume such as a disk image, properly allows each user in a multi-user system to have their own dock icon visibility settings, and reduces the number of user-visible strings that localizers have to translate.

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