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 <http://www.stone.com/TimeEqualsMoney/> 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;
...
@end
@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;
}
@end

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;
...
@end
@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;
}
@end

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 <http://www.omnigroup.com/~nygard/Projects/index.html>, 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) 
        inTableColumn:column];
        
        [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];
}

Conclusion

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


Andrew Stone, andrew@stone.com, is Chief Chef at Stone Design, http://www.stone.com, 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

PDFKey Pro 4.3 - Edit and print password...
PDFKey Pro can unlock PDF documents protected for printing and copying when you've forgotten your password. It can now also protect your PDF files with a password to prevent unauthorized access and/... Read more
Kodi 15.0.beta1 - Powerful media center...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
DiskCatalogMaker 6.4.12 - Catalog your d...
DiskCatalogMaker is a simple disk management tool which catalogs disks. Simple, light-weight, and fast. Finder-like intuitive look and feel. Super-fast search algorithm. Can compress catalog data... Read more
Macs Fan Control 1.3.0.0 - Monitor and c...
Macs Fan Control allows you to monitor and control almost any aspect of your computer's fans, with support for controlling fan speed, temperature sensors pane, menu-bar icon, and autostart with... Read more
Lyn 1.5.11 - Lightweight image browser a...
Lyn is a lightweight and fast image browser and viewer designed for photographers, graphic artists and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it... Read more
NeoOffice 2014.11 - Mac-tailored, OpenOf...
NeoOffice is a complete office suite for OS X. With NeoOffice, users can view, edit, and save OpenOffice documents, PDF files, and most Microsoft Word, Excel, and PowerPoint documents. NeoOffice 3.x... Read more
LaunchBar 6.4 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
Remotix 3.1.4 - Access all your computer...
Remotix is a fast and powerful application to easily access multiple Macs (and PCs) from your own Mac. Features Complete Apple Screen Sharing support - including Mac OS X login, clipboard... Read more
DesktopLyrics 2.6.6 - Displays current i...
DesktopLyrics is an application that displays the lyrics of the song currently playing in "iTunes" right on your desktop. The lyrics for the song have to be set in iTunes; DesktopLyrics does nothing... Read more
VOX 2.5.1 - Music player that supports m...
VOX is a beautiful music player that supports many filetypes. The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all... Read more

This Week at 148Apps: May 18-22, 2015
May Days at 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out above the... | Read more »
Biz Builder Delux (Games)
Biz Builder Delux 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Ah, there's nothing like the rhythmic bustle of a burgeoning business burg... especially when you're the one building it... | Read more »
Auroch Digital is Bringing Back Games Wo...
| Read more »
Blades of Brim is a New Endless Runner f...
SYBO Games, the minds behind the ever-popular Subway Surfers, have announced their latest project: Blades of Brim. [Read more] | Read more »
Carbo - Handwriting in the Digital Age...
Carbo - Handwriting in the Digital Age 1.0 Device: iOS Universal Category: Productivity Price: $3.99, Version: 1.0 (iTunes) Description: | Read more »
Draggy Dead (Games)
Draggy Dead 1.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.1 (iTunes) Description: Ditch your dead end job and take up a rewarding career in Grave Robbing today!Guide the recently deceased to a fun filled life of... | Read more »
Bad Dinos (Games)
Bad Dinos 1.0.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.0 (iTunes) Description: | Read more »
The Apple Watch isn't Great as a Fi...
| Read more »
Show the World What You See With Stre.am...
Live broadcasting is getting popular on mobile devices, which is why you can now get Stre.am, by Infinite Takes. [Read more] | Read more »
PhotoTime's 2.1 Update Adds Apple W...
The latest PhotoTime update is adding even more functionality to the handy photo organizing app. Yep, including Apple Watch support. [Read more] | Read more »

Price Scanner via MacPrices.net

12-inch MacBook stock status for Monday, May...
The new 12″ Retina MacBooks are still on backorder at The Apple Store with a 3-5 week waiting period. However, a few models are in stock today at Apple resellers. Stock is limited, so act now if you’... Read more
New 27-inch 3.3GHz 5K iMac in stock with free...
Adorama has the new 27″ 3.3GHz 5K iMac in stock today for $1999 including free shipping plus NY & NJ sales tax only. Adorama will include a free copy of Apple’s 3-year AppleCare Protection Plan. Read more
Memorial Day Weekend Sale: New 27-inch 3.3GHz...
Best Buy has the new 27″ 3.3GHz 5K iMac on sale for $1899.99 this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary... Read more
OtterBox Maximizes Portability, Productivity...
From the kitchen recipe book to the boarsroom presentation, the OtterBox Agility Tablet System turns tablets into one of the most versatile pieces of handheld technology available. Available now, the... Read more
Launch of New Car App Gallery and Open Develo...
Automatic, a company on a mission to bring the power of the Internet into every car, has announced the launch of the Automatic App Gallery, an app store for nearly every car or truck on the road... Read more
Memorial Day Weekend Sale: 13-inch 1.6GHz Mac...
Best Buy has the new 13″ 1.6GHz/128GB MacBook Air on sale for $849 on their online store this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders... Read more
Memorial Day Weekend Sale: 27-inch 3.5GHz 5K...
Best Buy has the 27″ 3.5GHz 5K iMac on sale for $2099.99 this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary.... Read more
Sale! 16GB iPad mini 3 for $349, save $50
B&H Photo has the 16GB iPad mini 3 WiFi on sale for $349 including free shipping plus NY sales tax only. Their price is $50 off MSRP, and it’s the lowest price available for this model. Read more
Price drop on 2014 15-inch Retina MacBook Pro...
B&H Photo has dropped prices on 2014 15″ Retina MacBook Pros by $200. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799.99 save $200 - 15″ 2.5GHz... Read more
With a Mission to Make Mobile Free, Scratch W...
Scratch Wireless, claiming to be the world’s first truly free mobile service, has announced the availability of a new Scratch-enabled Android smartphone, the Coolpad Arise. The smartphone is equipped... Read more

Jobs Board

Payments Counsel, *Apple* Pay (mobile payme...
**Job Summary** Apple is looking for an atto ey to join Apple 's Legal Department to support Apple Pay. **Key Qualifications** 7+ years of relevant experience Read more
Touch Hardware Design and Integration Enginee...
…Summary** Design, develop, and launch next-generation Touch solutions in the new Apple Watch product category. The Touch team develops cutting-edge Touch solutions and Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* TV Live Streaming Frameworks Test En...
**Job Summary** Work and contribute towards the engineering of Apple 's state-of-the-art products involving video, audio, and graphics in Interactive Media Group (IMG) at Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.