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

Microsoft Remote Desktop 8.0.16 - Connec...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
Spotify 1.0.4.90. - Stream music, create...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
djay Pro 1.1 - Transform your Mac into a...
djay Pro provides a complete toolkit for performing DJs. Its unique modern interface is built around a sophisticated integration with iTunes and Spotify, giving you instant access to millions of... Read more
Vivaldi 1.0.118.19 - Lightweight browser...
Vivaldi browser. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind that users are... Read more
Stacks 2.6.11 - New way to create pages...
Stacks is a new way to create pages in RapidWeaver. It's a plugin designed to combine drag-and-drop simplicity with the power of fluid layout. Features: Fluid Layout: Stacks lets you build pages... Read more
xScope 4.1.3 - Onscreen graphic measurem...
xScope is powerful set of tools that are ideal for measuring, inspecting, and testing on-screen graphics and layouts. Its tools float above your desktop windows and can be accessed via a toolbar,... Read more
Cyberduck 4.7 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Labels & Addresses 1.7 - Powerful la...
Labels & Addresses is a home and office tool for printing all sorts of labels, envelopes, inventory labels, and price tags. Merge-printing capability makes the program a great tool for holiday... Read more
teleport 1.2.1 - Use one mouse/keyboard...
teleport is a simple utility to let you use one single mouse and keyboard to control several of your Macs. Simply reach the edge of your screen, and your mouse teleports to your other Mac! The... Read more
Apple iMovie 10.0.8 - Edit personal vide...
With an all-new design, Apple iMovie lets you enjoy your videos like never before. Browse your clips more easily, instantly share your favorite moments, and create beautiful HD movies and Hollywood-... Read more

Use Batting Average and the Apple Watch...
Batting Average, by Pixolini, is designed to help you manage your statistics. Every time you go to bat, you can use your Apple Watch to track  your swings, strikes, and hits. [Read more] | Read more »
Celebrate Studio Pango's 3rd Annive...
It is time to party, Pangoland pals! Studio Pango is celebrating their 3rd birthday and their gift to you is a new update to Pangoland. [Read more] | Read more »
Become the World's Most Important D...
Must Deliver, by cherrypick games, is a top-down endless-runner witha healthy dose of the living dead. [Read more] | Read more »
SoundHound + LiveLyrics is Making its De...
SoundHound Inc. has announced that SoundHound + LiveLyrics, will be one of the first third-party apps to hit the Apple Watch. With  SoundHound you'll be able to tap on your watch and have the app recognize the music you are listening to, then have... | Read more »
Adobe Joins the Apple Watch Lineup With...
A whole tidal wave of apps are headed for the Apple Watch, and Adobe has joined in with 3 new ways to enhance your creativity and collaborate with others. The watch apps pair with iPad/iPhone apps to give you total control over your Adobe projects... | Read more »
Z Steel Soldiers, Sequel to Kavcom'...
Kavcom has released Z Steel Soldiers, which continues the story of the comedic RTS originally created by the Bitmap Brothers. [Read more] | Read more »
Seene Lets You Create 3D Images With You...
Seene, by Obvious Engineering, is a 3D capture app that's meant to allow you to create visually stunning 3D images with a tap of your finger, and then share them as a 3D photo, video or gif. [Read more] | Read more »
Lost Within - Tips, Tricks, and Strategi...
Have you just downloaded Lost Within and are you in need of a guiding hand? While it’s not the toughest of games out there you might still want some helpful tips to get you started. [Read more] | Read more »
Entertain Your Pet With Your Watch With...
The Petcube Camera is a device that lets you use live video to check in on your pet, talk to them, and play with them using a laser pointer - all while you're away. And the Petcube app is coming to the Apple Watch, so you'll be able to hang out with... | Read more »
Now You Can Manage Your Line2 Calls With...
You'll be able to get your Line2 cloud phone service on the Apple Watch very soon. The watch app can send and receive messages using hands-free voice dictation, or by selecting from a list of provided responses. [Read more] | Read more »

Price Scanner via MacPrices.net

Intel Compute Stick: A New Mini-Computing For...
The Intel Compute Stick, a new pocket-sized computer based on a quad-core Intel Atom processor running Windows 8.1 with Bing, is available now through Intel Authorized Dealers across much of the... Read more
Heal to Launch First One-Touch House Call Doc...
Santa Monica, California based Heal, a pioneer in on-demand personal health care services — will offer the first one-touch, on-demand house call doctor app for the Apple Watch. Heal’s Watch app,... Read more
Mac Notebooks: Avoiding MagSafe Power Adapter...
Apple Support says proper usage, care, and maintenance of Your Mac notebook’s MagSafe power adapter can substantially increase the the adapter’s service life. Of course, MagSafe itself is an Apple... Read more
12″ Retina MacBook In Shootout With Air And P...
BareFeats’ rob-ART morgan has posted another comparison of the 12″ MacBook with other Mac laptops, noting that the general goodness of all Mac laptops can make which one to purchase a tough decision... Read more
FileMaker Go for iPad and iPhone: Over 1.5 Mi...
FileMaker has announced that its FileMaker Go for iPad and iPhone app has surpassed 1.5 million downloads from the iTunes App Store. The milestone confirms the continued popularity of the FileMaker... Read more
Sale! 13-inch 2.7GHz Retina MacBook Pro for $...
 Best Buy has the new 2015 13″ 2.7GHz/128GB Retina MacBook Pro on sale for $1099 – $200 off MSRP. Choose free shipping or free local store pickup (if available). Price for online orders only, in-... Read more
Minimalist MacBook Confirms Death of Steve Jo...
ReadWrite’s Adriana Lee has posted a eulogy for the “Digital Hub” concept Steve Jobs first proposed back in 2001, declaring the new 12-inch MacBook with its single, over-subscribed USB-C port to be... Read more
13-inch 2.7GHz Retina MacBook Pro for $1234 w...
Adorama has the 13″ 2.7GHz/128GB Retina MacBook Pro in stock for $1234.99 ($65 off MSRP) including free shipping plus a free LG external DVD/CD optical drive. Adorama charges sales tax in NY & NJ... Read more
13-inch 2.5GHz MacBook Pro available for $999...
 Adorama has the 13-inch 2.5GHz MacBook Pro on sale for $999 including free shipping plus NY & NJ sales tax only. Their price is $100 off MSRP. Read more
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store is offering Apple Certified Refurbished Mac Pros 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... Read more

Jobs Board

*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
*Apple* Support Technician IV - Jack Henry a...
Job Description Jack Henry & Associates is seeking an Apple Support Technician. This position while acting independently, ensures the proper day-to-day control of Read more
*Apple* Client Systems Solution Specialist -...
…drive revenue and profit in assigned sales segment and/or region specific to the Apple brand and product sets. This person will work directly with CDW Account Managers Read more
*Apple* Software Support - Casper (Can work...
…experience . Full knowledge of Mac OS X and prior . Mac OSX / Server . Apple Remote Desktop . Process Documentation . Ability to prioritize multiple tasks in a fast pace Read more
*Apple* Software Support - Xerox Corporation...
…Imaging experience Full knowledge of Mac OS X and prior Mac OSX / Server Apple Remote Desktop Process Documentation Ability to prioritize multiple tasks in a fast pace Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.