TweetFollow Us on Twitter

Takes All Sorts

Volume Number: 18 (2002)
Issue Number: 8
Column Tag: Mac OS X

Takes All Sorts

Make Your TableViews Autosort!

by Andrew C. Stone

One of the coolest pieces of object technology in the Cocoa bag of tricks is the NSTableView, and its daughter, NSOutlineView. The tableView lets you display a list of items with various properties. As in a spreadsheet, it displays rows of information - anything from simple text to graphics or even quicktime movies! Once you learn the fundamentals of the tableView and the outlineView, they'll quickly become some of your favorite user interface objects.

This article will take the NSTableView further, and show you how to add "auto sort" to your tableView, and the objects it represents. It assumes you have read the documentation for NSTableView and its companion class NSTableColumn and perhaps already have an app with an NSTableView of your own. You can try out this sort idea in Apple's Mail. A Mail Box shows a tableView of the list of messages, sender, subject, date, size, etc:

Figure 1. You can play with quick sort feature in Apple's Mail application.

When you click on the title cell of a column, an arrow appears to show direction of the sort, the cell is highlighted, and the messages are sorted on that key. If you click the title cell of that same column again, it toggles the sort to reverse its direction: if it was an ascending sort, now it's a descending sort. Sorting mail by subject is particularly interesting for deleting spam en masse!

When Time Equals Money...

When preparing TimeEqualsMoney 2.0 <> this spring, I decided users would love to be able to sort their time and expense entries on any key, in either direction with a simple click. So I reread the documentation Apple provides on the NSTableView class. I highly recommend actually reading the .h files! It's amazing how much stuff is already anticipated for you! There is a delegate method, - (void) tableView:(NSTableView*)tv didClickTableColumn:(NSTableColumn *)tableColumn. So, it seemed, I simply had to implement this method in my NSWindowController subclass, which is architecturally a sound choice for the NSTableView delegate. However, the method was simply not being called when I clicked on the column header cell. It turns out, and I noted this heavily in my code, that if neither column reodering nor column selection is selected in Interface Builder's NSTableView inspector, then the method is not called. Turning on column reordering was a simple fix and a desired feature! You can, of course, also call one of these methods programmatically with a parameter of YES:

- (void)setAllowsColumnReordering:(BOOL)flag;
- (void)setAllowsColumnSelection:(BOOL)flag;

Following on the Model-View-Controller pattern that I have discussed in previous articles on Cocoa architecture, I decided to store the sort column, and its direction in my NSDocument subclass, as well as make it responsible for the sorting of its items. This way, you can undo the sort, automatically mark the document as unsaved as well as save the sort between sessions. The user clicks the tableView column header, the window controller then sets the document's sort key, or direction if the key was already set to that column. Then the document tells itself to sort, which tells its NSMutableArray of entries to sort its contents. Finally, the document tells its window controllers to reload the tableView, which updates the interface to display the new sort order:

Figure 2. This tableView lets you click a column header to sort on that key - up or down.

Model Behavior

The implementation of the actual sort is trivial: just ask the list to sort itself based on asking its elements to sort using a selector: [list sortUsingSelector:@selector(compare:)];

During the list's sorting procedure, it repeatedly calls, in this case, compare: on one list item against another.

I like to just reuse the Kit's compare: which is implemented in NSString, NSDate, NSCell, NSValue, etc:

- (NSComparisonResult)compare:(id)other;

The NSComparisonResult has these three values: NSOrderedAscending = -1, NSOrderedSame = 0, NSOrderedDescending = 1. Since so many objects reply to compare:, you might implement it something like this in your data object, given that the sort key is the same string as the column identifiers, and you have various numbers, dates, strings and even booleans:

// the Data MODEL - the document has a list of these entities:
@interface PieceWork : NSObject <NSCopying>
    NSCalendarDate *startTime;
    NSString *description;
    NSTimeInterval timeOnJob;
    float _rate;
    BOOL paid;
    id owner;
- (NSComparisonResult)compare:(id)other;
- (void)setOwner:(id)ownsMe;
- (NSCalendarDate *)startTime;
- (NSTimeInterval)timeOnJob;
- (NSString *)workDescription;
- (float)hoursOnJob;
- (float)rate;
- (BOOL)paid;
@implementation PieceWork
- (NSComparisonResult)compare:(id)other {
    BOOL isDescending = [owner sortIsDescending];
    NSString *key = [owner sortColumn];
   // now determine which one is first based on sort direction:
    PieceWork *first = isDescending ? other : self;
    if (first == other) other = self;
    if ([key isEqualToString:@"TimeOnJob"]) {
        return [[NSNumber numberWithFloat:[other timeOnJob]] compare: 
        [NSNumber numberWithFloat:[first timeOnJob]]];
    } else if ([key isEqualToString:@"Date"]) {
        return [[other startTime] compare: [first startTime]];
    } else if ([key isEqualToString:@"Description"]) {
// Very handy macro:
#define IS_NULL(s) (!s || [s isEqualToString:@""])
            if (IS_NULL([other workDescription])) return NSOrderedDescending;
            if (IS_NULL([first workDescription])) return NSOrderedAscending;
// people prefer upper and lower case mixed, unlike UNIX:
        return [[other workDescription] caseInsensitiveCompare:[first workDescription]];
    } else if ([key isEqualToString:@"Paid"]) {
        return [[NSNumber numberWithBool:[other paid]] compare:[NSNumber 
        numberWithBool:[first paid]]];
    return 0;

Here are the relevant instant variables and methods in the NSDocument subclass:

@interface MyDocument : NSDocument {
    NSMutableArray *_workList;
    NSString *_sortColumn;
    BOOL _sortIsDescending;
.   ...
- (void)sort;
- (NSArray *)workList;
- (void)setSortColumn:(NSString *)identifier;
- (NSString *)sortColumn;
- (void)setSortIsDescending:(BOOL)whichWay;
- (BOOL)sortIsDescending;
@implementation MyDocument
- (void)sort:(NSMutableArray *)list {
    [list makeObjectsPerformSelector:@selector(setOwner:) withObject:self];
    [list sortUsingSelector:@selector(compare:)];  // asks us for how!!
- (void) sort {
    if (NOT_NULL(_sortColumn)) {
        [self sort:_workList];
        [[self windowControllers] makeObjectsPerformSelector:@selector(updateTotalsAndReload)];
- (void)setSortColumn:(NSString *)identifier {
    if (![identifier isEqualToString:_sortColumn]) {
        [[[self undoManager] prepareWithInvocationTarget:self] setSortColumn:_sortColumn];
    [_sortColumn release];
    _sortColumn = [identifier copyWithZone:[self zone]];
        [[self undoManager] setActionName:NSLocalizedStringFromTable(@"Sort",@"TimeCard",@"title of 
        undo the sort action")];
- (NSString *)sortColumn {
    return _sortColumn;
- (void)setSortIsDescending:(BOOL)whichWay {
    if (whichWay != _sortIsDescending) {
        [[[self undoManager] prepareWithInvocationTarget:self] setSortIsDescending:_sortIsDescending];
    _sortIsDescending = whichWay;
        [[self undoManager] setActionName:NSLocalizedStringFromTable(@"Sort 
        Direction",@"TimeCard",@"title of undo the sort up or down action")];
- (BOOL)sortIsDescending {
    return _sortIsDescending;
- (NSArray *)workList { return _workList; }
- (void)setWorkList:(NSMutableArray *)list {
    [[[self undoManager] prepareWithInvocationTarget:self] setWorkList:_workList];
    [_workList release];
    if (NOT_NULL(_sortColumn)) [self sort:list];
    _workList = [list mutableCopyWithZone:[self zone]];
    [_workList makeObjectsPerformSelector:@selector(setOwner:) withObject:self];
    [[self windowControllers] makeObjectsPerformSelector:@selector(updateTotalsAndReload)];
    [[self undoManager] setActionName:NSLocalizedStringFromTable(@"Work Change", @"TimeCard", 
    @"Action name for changing worklist")];
// And don't forget to actually archive and read the sort info
// I highly recommended using human readable XML dictionaries:
- (NSMutableDictionary *)workDocumentDictionary {
    NSMutableDictionary *doc = [NSMutableDictionary dictionary];
        unsigned i, c = [_workList count];
        if (NOT_NULL(_sortColumn)) [doc setObject:_sortColumn forKey:SortNameKey];
        if (_sortIsDescending) [doc setObject:@"YES" forKey:SortDescendingKey];
       return doc;
- (BOOL)loadDataRepresentation:(NSData *)data ofType:
                                                      (NSString *)type {
    if ([type isEqualToString:DocumentType]) {
 NSDictionary *doc = [self workDocumentDictionaryFromData:data];
        id obj;
        obj = [doc objectForKey:SortNameKey];
        if (obj) {
            [self setSortColumn:obj];
      obj = [doc objectForKey:SortDescendingKey];
        if (obj) {
            _sortIsDescending = [@"YES" isEqualToString:obj];
        return YES;
  return NO;

Control Freak

Finally, we come to the meat of the matter in our NSWindowController subclass which is our NSTableView's dataSource as well as delegate.

@interface JobWindowController : NSWindowController 
    IBOutlet NSTableView *tableView;
    NSImage *descendingSortingImage;
    NSImage *ascendingSortingImage;

We have work to do in our window initialization method that gets called when the Interface has loaded, awakeFromNib. We want to get the images that we shall display when a sort is made. Using class-dump as described in my iPhoto Exporter bundle article <>, you might note that there are hidden, private Apple internal API to access the images to indicate ascending or descending sorts! Since one should absolutely never rely on hidden API to not dissolve into the ether in subsequent system releases, always bracket the use of these methods with a "respondsToSelector:" query, and provide backup images of your own:

- (void)awakeFromNib
    // private images:
    if ([[NSTableView class] respondsToSelector:@selector(_defaultTableHeaderSortImage)])
    ascendingSortingImage = [[NSTableView class] _defaultTableHeaderSortImage];
    else ascendingSortingImage = [[NSImage imageNamed:@"ascendingSort"] retain];
    if ([[NSTableView class] respondsToSelector:@selector(_defaultTableHeaderReverseSortImage)])
    descendingSortingImage = [[NSTableView class] _defaultTableHeaderReverseSortImage];
    else descendingSortingImage = [[NSImage imageNamed:@"descendingSort"] retain];

If you allow users to move and resize columns, then you definitely want to additionaly call these two methods in awakeFromNib - this will reestablish their preferences and give the system a name to save the column order and sizes.

    [tableView setAutosaveTableColumns:YES];
    [tableView setAutosaveName:@"WorkTable"];

So, now we're ready to implement the delegate method which gets called when the column title cell is clicked. The one fine point is that we want to make a note of which item was selected before the sort, so we can reselect it after the sort (its row number may have changed after the sort). We ask the tableView if it already has an image in that column, thus indicating that we need to toggle the direction, otherwise, we'll set the new sort key. The actual work of setting up the tableView's header hilighting is done in updateTableHeaderToMatchCurrentSort. This is factored into a separate method so we can also call it when loading a document to restore last saved sort state.

// BIG COCOA NOTE: if column reordering or column selection is not on
// then this doesn't get called!!
- (void) tableView:(NSTableView*)tv didClickTableColumn:(NSTableColumn *)tableColumn {
    NSImage *sortOrderImage = [tv indicatorImageInTableColumn:tableColumn];
    NSString *columnKey = [tableColumn identifier];
    MyDocument *doc = [self document];
    PieceWork *work = [self selectedWork];
    // If the user clicked the column which already has the sort indicator
    // then just flip the sort order.
    if (sortOrderImage || columnKey == [doc sortColumn]) {
        [doc setSortIsDescending:![doc sortIsDescending]]; 
    } else {
        [doc setSortColumn:columnKey];
    [self updateTableHeaderToMatchCurrentSort];
    // now do it - doc calls us back when done
    [doc sort];
    // but reselect the one previously selected:
    if (work) [self selectWork:work];

This method updates the state of the NSTableColumn by first clearing all cells, and then setting the correct image and hilighting on the column to sort by, if any:

- (void)updateTableHeaderToMatchCurrentSort {
    BOOL isDescending = [[self document] sortIsDescending];
    NSString *key = [[self document] sortColumn];
    NSArray *a = [tableView tableColumns];
    NSTableColumn *column = [tableView tableColumnWithIdentifier:key];
    unsigned i = [a count];
    while (i-- > 0) [tableView setIndicatorImage:nil inTableColumn:[a objectAtIndex:i]];
    if (NOT_NULL(key)) {
        [tableView setIndicatorImage:(isDescending ? ascendingSortingImage:descendingSortingImage) 
        [tableView setHighlightedTableColumn:column];
    } else [tableView setHighlightedTableColumn:nil];

And our helper functions to make the code neat and compact:

- (NSArray *)workList {
   return [[self document] workList];
- (void)updateTotalsAndReload {
// other ui:
//    [self updateTotals];
    [tableView reloadData];
- (PieceWork *)selectedWork {
   NSArray *workList = [self workList];
   int row = [tableView selectedRow];
   if (row > -1 && row < [workList count]) return [workList objectAtIndex:row];
   return nil;
- (void)selectWork:(PieceWork *)work {
    NSArray *a = [self workList];
    unsigned i = [a indexOfObject:work];
    if (i != NSNotFound) [self selectRow:i];

Devil in the Details

So, now we got sorting working, what sort of problems might we run into? Let's say a user edits the field of an entry in the sorted column. Upon finishing editing, they may have changed the relative order of that entry, requiring a new sort, and a reloading of the tableView again! We can check if we have the sorted column when the data gets set in - tableView:setObjectValue:forTableColumn:row:

- (void)tableView:(NSTableView *)tv setObjectValue:(id)object 
forTableColumn:(NSTableColumn *)tc row:(int)row;
        NSArray *workList = [self workList];
        NSString *ident = [tc identifier];
        if (tv == tableView) {
            PieceWork *work = [workList objectAtIndex:row];
            if ([ident isEqual:@"Description"]) {
                [work setWorkDescription:object];
                [self sortIfSortedOn:ident work:work];
           } else if ....

Isn't the devil in the details? Because the tableView will want to "select next" after setObjectValue: is called, the wrong row might be selected if the sort changed the currently selected item's row. By calling this method, we'll first end editing on the tableView so any inadvertent select next is foiled. Note the delay of 0.0 seconds which means to schedule the call of the method after the current event loop finishes:

- (void)afterSort:(PieceWork *)work {
    [[self window] makeFirstResponder:[self window]];
    [self selectWork:work];
- (void)sortIfSortedOn:(NSString *)ident work:(PieceWork *)work {
    if ([[[self document] sortColumn] isEqualToString:ident])  {
        int oldPosition
        [[self window] makeFirstResponder:[self window]];
        [[self document] sort];
        [self performSelector:@selector(afterSort:) withObject:work afterDelay:0.0];
    } else [self updateTotalsAndReload];


Sorting is something users expect tableViews to do now - and with a little effort, all of your tableViews can sort themselves!

Andrew Stone,, is Chief Chef at Stone Design,, has this to say about Cocoa and Stone Studio with all due respect to Gary Snyder's Turtle Island, "It's objects all the way down" .


Community Search:
MacTech Search:

Software Updates via MacUpdate

Shimo - VPN client – for everyon...
Shimo is the most versatile VPN client for OS X and it enables really everybody to master secure network. It supports more protocols than any other VPN application out there! CiscoVPN, AnyConnect,... Read more
Dash 3.4.0 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
AirRadar 3.1.9 - $9.95
With AirRadar, scanning for wireless networks is now easier and more personalized! It allows you to scan for open networks and tag them as favourites or filter them out. View detailed network... Read more
Printopia 2.1.22 - Share Mac printers wi...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
SteerMouse 5.0 - Powerful third-party mo...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
Alarm Clock Pro 10.2.5 - $19.95
Alarm Clock Pro isn't just an ordinary alarm clock. Use it to wake you up in the morning, send and compose e-mails, remind you of appointments, randomize the iTunes selection, control an internet... Read more
Cocktail 10.1 - General maintenance and...
Cocktail is a general purpose utility for macOS that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
RapidWeaver 7.1.7 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
MacCleanse 5.1.6 - $29.95
MacCleanse is the product of thousands of hours of intense research and development. It meticulously scans all of the nooks and crannies of a computer for unnecessary junk that can take up huge... Read more
Slack 2.3.0 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.3.0: Note: Now requires OS X 10.8 or later New The app... Read more

Latest Forum Discussions

See All

4 addictive clicker games like Best Fien...
Clickers are passive games that take advantage of basic human psychology to suck you in, and they're totally unashamed of that. As long as you're aware that this game has been created to take hold of your brain and leave you perfectly content to... | Read more »
Smile Inc. Guide: How not to die on the...
As if Mondays weren't bad enough, at Smile Inc. you have to deal with giant killer donuts, massive hungry staplers, and blasting zones. It's not exactly a happy, thriving work environment. In fact, you'll be lucky to survive the nine to five.... | Read more »
Oh...Sir! The Insult Simulator (Games)
Oh...Sir! The Insult Simulator 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
WitchSpring2 (Games)
WitchSpring2 1.27 Device: iOS Universal Category: Games Price: $3.99, Version: 1.27 (iTunes) Description: This is the story of Luna, the Moonlight Witch as she sets out into the world. This is a sequel to Witch Spring. Witch Spring 2... | Read more »
4 popular apps getting a Halloween makeo...
'Tis the season for all things spooky. So much, so, in fact, that even apps are getting into the spirt of things, dressing up in costume and spreading jack o' lanterns all about the place. These updates bring frightening new character skins, scary... | Read more »
Pokémon GO celebrates Halloween with can...
The folks behind Pokémon GO have some exciting things planned for their Halloween celebration, the first in-game event since it launched back in July. Starting October 26 and ending on November 1, trainers will be running into large numbers of... | Read more »
Best Fiends Forever Guide: How to collec...
The fiendship in Seriously's hit Best Fiends has been upgraded this time around in Best Fiends Forever. It’s a fast-paced clicker with lots of color and style--kind of reminiscent of a ‘90s animal mascot game like Crash Bandicoot. The game... | Read more »
5 apps for the budding mixologist
Creating your own cocktails is something of an art form, requiring a knack for unique tastes and devising interesting combinations. It's easy to get started right in your own kitchen, though, even if you're a complete beginner. Try using one of... | Read more »
5 mobile strategy games to try when you...
Strategy enthusiasts everywhere are celebrating the release of Civilization VI this week, and so far everyone seems pretty satisfied with the first full release in the series since 2010. The series has always been about ultra-addictive gameplay... | Read more »
Popclaire talk to us about why The Virus...
Humanity has succumbed to a virus that’s spread throughout the world. Now the dead have risen with a hunger for human flesh, and all that remain are a few survivors. One of those survivors has just called you for help. That’s the plot in POPCLAIRE’... | Read more »

Price Scanner via

Apple refurbished 2015 13-inch MacBook Airs a...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2015 13″ 1.6GHz/4GB/128GB MacBook... Read more
64GB Apple TV on sale for $159, save $40
Best Buy has the 64GB Apple TV on sale for $40 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store price may... Read more
EyeQue Introduces iOS And Android Based Advan...
Affordable vision technologies developers EyeQue have announced what they claim to be the world’s most advanced intelligent vision solution, pitched as enabling anyone, anywhere to easily and... Read more
Smartwatch Market Tanks, Declining 51.6% in 2...
The worldwide smartwatch market experienced a round of growing pains in the third quarter of 2016 (3Q16), resulting in a year-over-year decline in shipment volumes. According to data from the... Read more
CAZE announces Ultra Thin Glass Screen Protec...
Hong Kong based CAZE has announced its first ultra thin glass screen protector, the Glazz Pro for iPhone 7/7 Plus. Glazz Pro is made from chemically reinforced glass with an anti-fingerprint... Read more
11-inch MacBook Airs on sale for up to $120 o...
Newegg has 11″ MacBook Airs on sale for up to $120 off MSRP. Shipping is free: - 11″ 1.6GHz/128GB MacBook Air: $799.99 $100 off MSRP - 11″ 1.6GHz/256GB MacBook Air: $979 $120 off MSRP Read more
Up to $300 off Macs, $20 off iPads with Apple...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Apple’s Thursday “Hello Again” Event A Largel...
KGI Securities analyst Ming-Chi Kuo, who has a strong record of Apple hardware prediction accuracy, forecasts in a new note to investors released late last week that a long-overdue redo of the... Read more
12-inch Retina MacBooks on sale for $100 off...
Amazon has 2016 12″ Apple Retina MacBooks on sale for $100 off MSRP. Shipping is free: - 12″ 1.1GHz Silver Retina MacBook: $1199.99 $100 off MSRP - 12″ 1.1GHz Gold Retina MacBook: $1199.99 $100 off... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The following... Read more

Jobs Board

Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 52812872 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Solutions Read more
Lead *Apple* Solutions Consultant - Apple (...
# Lead Apple Solutions Consultant Job Number: 52812906 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** The Lead ASC is an Read more
*Apple* Retail - Multiple Positions- Towson,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.