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    copied!<pre><code>// This looked like the best thread to post this. // This is incomplete skeleton example of NSDocument/NSUndoManager usage. // Use at your own risk // Ultimately, would love if Apple reviewed/corrected this and added correct sample code to their docs. // I put pseudo code in implementation specific spots: // "... implementation specific ..." // "... implement something inherently dangerous... loading your data from a file" // "... implement something inherently dangerous... commit changes to a file ..." // "... in my implementation, I prompt user with save/quit options when edit window is closed ..." // // Apple's documentation states that NSDocumentController should *rarely* be subclassed, // but Apple fails to provide sample code to accomplish what you need. // After trying to subclass NSDocumentController, I decided to rip all that code out. // What I really needed, in my case, was this: // @interface NSObject(NSApplicationDelegate) // - (BOOL)application:(NSApplication *)sender openFile:(NSString *)filename // // My requirements in a nutshell: // NSUndoManager, only allow 1 document open at a time (for now), multiple editing windows for 1 document, // automatically save to temporary file, ability to quit and relaunch without saving, // Custom "open", "save", "save as", "revert to saved", etc... MyDocumentController // subclass below provides a simple way to bypass much of the NSDocumentController // file dialogs, but still use other features of NSDocument (like track unsaved changes). // Override only "NSDocumentController documentForURL". /* your NSDocument subclass MUST be defined in your Info.plist. If you don't, Lion will complain with a NSLog message that looks like this: -[NSDocumentController openDocumentWithContentsOfURL:display:completionHandler:] failed during state restoration. Here's the error: Error Domain=NSCocoaErrorDomain Code=256 "The document “blah.myfiletype” could not be opened. cannot open files in the “blah Document” format." In this example, files of type .myfiletype are associated with my NSDocument subclass Personally, I hate having to put a class name in my Info.plist, because its not maintainable! Note to Apple developers: if you are going to force us to do this, then pleasssse make sure that an XCode search "In Project" for "MyDocument" finds the entry in the plist file! Oh wow, I just answered my own question: Apple! please make "All candidate files" the default option for search! MyDocument: &lt;key&gt;CFBundleDocumentTypes&lt;/key&gt; &lt;array&gt; &lt;dict&gt; &lt;key&gt;CFBundleTypeName&lt;/key&gt; &lt;string&gt;My Funky App File&lt;/string&gt; &lt;key&gt;NSDocumentClass&lt;/key&gt; &lt;string&gt;MyDocument&lt;/string&gt; &lt;key&gt;CFBundleTypeExtensions&lt;/key&gt; &lt;array&gt; &lt;string&gt;myfiletype&lt;/string&gt; &lt;/array&gt; &lt;key&gt;CFBundleTypeIconFile&lt;/key&gt; &lt;string&gt;My_File_Icon.icns&lt;/string&gt; &lt;key&gt;CFBundleTypeRole&lt;/key&gt; &lt;string&gt;Editor&lt;/string&gt; &lt;/dict&gt; &lt;/array&gt; */ #define kMyFileTypeExtension @"myfiletype" @interface MyDocument : NSDocument { } - (void) registerForUndoGrouping; - (NSString *)filePath; // convenience function - (void) setFilePath: (NSString *)filePath; // convenience function + (BOOL) openMyDocument: (NSString *)filename; // class method @end extern int gWantsToQuit; // global indicator that it's time to stop drawing/updating // track my startup state so I can control order of initialization, and so I don't // waste time drawing/updating before data is available. enum // MyLaunchStatus { kFinishedPreWaking = 0x01, // step 1: applicationWillFinishLaunching called kFinishedOpenFile = 0x02, // step 2: (optionally) application:openFile: called (important for detecting double-click file to launch app) kFinishedWaking = 0x04, // step 3: NSApp run loop ready to run. applicationDidFinishLaunching kFinishedPreLaunchCheck = 0x08, // step 4: error recovery check passed kFinishedLoadingData = 0x10, // step 5: data loaded kFinishedAndReadyToDraw = 0x20, // step 6: run loop ready for drawing }; typedef NSUInteger MyLaunchStatus; #pragma mark - @interface MyAppController : NSResponder &lt;MidiProtocol, NSOpenSavePanelDelegate, NSTextFieldDelegate, NSWindowDelegate&gt; MyDocument *toDocument; @end #pragma mark - @implementation MyDocument - (id)init { if ( !(self = [super init]) ) return self; return self; } - (void) registerForUndoGrouping { [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(beginUndoGroup:) name:NSUndoManagerDidOpenUndoGroupNotification object:nil]; } - (void)canCloseDocumentWithDelegate:(id)delegate shouldCloseSelector:(SEL)shouldCloseSelector contextInfo:(void *)contextInfo { if ( [[MyAppController instance] windowShouldClose: delegate] ) if ( [delegate respondsToSelector:@selector(close)] ) [delegate close]; //[delegate performSelector:shouldCloseSelector]; //if ( [delegate isKindOfClass:[NSWindow class]] ) // [delegate performClose:self]; // :self]; return; // handled by [[MyAppController instance] windowShouldClose:(id)sender } - (void)shouldCloseWindowController:(NSWindowController *)windowController delegate:(id)delegate shouldCloseSelector:(SEL)shouldCloseSelector contextInfo:(void *)contextInfo { if ( [[MyAppController instance] windowShouldClose: [windowController window]] ) if ( [[windowController window] respondsToSelector:@selector(close)] ) [[windowController window] close]; } - (void) beginUndoGroup: (NSNotification *)iNotification { NSUndoManager *undoMgr = [self undoManager]; if ( [undoMgr groupingLevel] == 1 ) { // do your custom stuff here } } // convenience functions: - (NSString *)filePath { return [[self fileURL] path]; } - (void) setFilePath: (NSString *)filePath { if ( [filePath length] ) [self setFileURL:[NSURL fileURLWithPath: filePath]]; else [self setFileURL:nil]; } - (BOOL)validateUserInterfaceItem:(id &lt;NSValidatedUserInterfaceItem&gt;)anItem { if ( [self isDocumentEdited] &amp;&amp; [anItem action] == @selector(revertDocumentToSaved:) ) return YES; BOOL retVal = [super validateUserInterfaceItem:(id &lt;NSValidatedUserInterfaceItem&gt;)anItem]; return retVal; } - (IBAction)revertDocumentToSaved:(id)sender { NSInteger retVal = NSRunAlertPanel(@"Revert To Saved?", [NSString stringWithFormat: @"Revert to Saved File %@?", [self filePath]], @"Revert to Saved", @"Cancel", NULL); if ( retVal == NSAlertDefaultReturn ) [[MyAppController instance] myOpenFile:[self filePath]]; } + (BOOL) openMyDocument: (NSString *)filename { if ( ![[filename pathExtension] isEqualToString: kMyAppConsoleFileExtension] ) return NO; // If the user started up the application by double-clicking a file, the delegate receives the application:openFile: message FIRST MyLaunchStatus launchStatus = [[MyAppController instance] isFinishedLaunching]; BOOL userDoubleClickedToLaunchApp = !( launchStatus &amp; kFinishedPreLaunchCheck ); MyDocument *currDoc = [[MyAppController instance] document]; NSString *currPath = [currDoc filePath]; NSInteger retVal; NSLog( @"open file %@ currPath %@ launchStatus %d", filename, currPath, launchStatus ); if ( userDoubleClickedFileToLaunchApp ) { // user double-clicked a file to start MyApp currPath = [[NSUserDefaults standardUserDefaults] objectForKey:@"LastSaveFile"]; if ( [currPath isEqualToString: filename] ) { sWasAlreadyOpen = YES; if ( [[[NSUserDefaults standardUserDefaults] objectForKey:@"isDocumentEdited"] boolValue] == YES ) { retVal = NSRunAlertPanel(@"Open File", @"Revert to Saved?", @"Revert to Saved", @"Keep Changes", @"Quit", NULL); if ( retVal == NSAlertDefaultReturn ) { [[MyAppController instance] myOpenFile:filename]; } else if ( retVal == NSAlertOtherReturn ) exit(0); } // proceed with normal startup if ( currDoc ) return YES; else return NO; } } if ( !(launchStatus &amp; kFinishedPreLaunchCheck ) ) // not done launching return YES; // startup in whatever state we were before if ( [currPath isEqualToString: filename] ) { sWasAlreadyOpen = YES; NSLog( @"is edited %d currDoc %@", [currDoc isDocumentEdited], currDoc ); if ( [currDoc isDocumentEdited] ) [currDoc revertDocumentToSaved:self]; // will prompt else // document is already open, so do what Apple's standard action is... [currDoc showWindows]; } else { if ( [currDoc isDocumentEdited] ) retVal = NSRunAlertPanel(@"Open File", [NSString stringWithFormat: @"The current file has unsaved changes. Discard unsaved changes and switch to file '%@'?", filename], @"Discard unsaved changes and switch to file", @"Keep Current", NULL); else retVal = NSRunAlertPanel(@"Switch to File", [NSString stringWithFormat: @"Switch to File '%@'?\n\nCurrent file '%@'", filename, currfilePath ? currfilePath : @"Untitled"], @"Switch", @"Keep Current", NULL); if ( retVal == NSAlertDefaultReturn ) [[MyAppController instance] myOpenFile:filename]; } // user cancelled if ( currDoc ) return YES; else return NO; } // Note: readFromURL is here for completeness, but it should never be called, // because we override NSDocumentController documentForURL below. - (BOOL)readFromURL:(NSURL *)absoluteURL ofType:(NSString *)typeName error:(NSError **)outError { if ( outError ) *outError = nil; if ( ![typeName isEqualToString: kMyFileTypeExtension ] ) // return NO; return YES; } // Note: writeToURL is here for completeness, but it should never be called, // because we override NSDocumentController documentForURL below. - (BOOL)writeToURL:(NSURL *)absoluteURL ofType:(NSString *)typeName error:(NSError **)outError { if ( outError ) *outError = nil; return YES; } @end // kpk migrating slowly toward NSDocument framework // (currently most functionality is in MyAppController) // Must bypass default NSDocumentController behavior to allow only 1 document // and keep MyAppController responsible for read, write, dialogs, etc. @implementation MyDocumentController // this should be the only override needed to bypass NSDocument dialogs, readFromURL, // and writeToURL calls. // Note: To keep Lion happy, MainInfo.plist and Info.plist must define "MyDocument" for key "NSDocumentClass" - (id)documentForURL:(NSURL *)absoluteURL { MyDocument *currDoc = [[MyAppController instance] document]; if ( [[currDoc filePath] isEqualToString: [absoluteURL path]] ) return currDoc; else return nil; } @end #pragma mark - @implementation MyAppController static MyAppController *sInstance; + (MyAppController *)instance { return sInstance; // singleton... why is this not in all Apple's sample code? } // called by main.mm before MyAppController (or NSApp for that matter) is created. // need to init some global variables here. + (void) beforeAwakeFromNib { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; ... implementation specific ... // disable fancy stuff that slows launch down [[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithBool:NO] forKey: @"NSAutomaticWindowAnimationsEnabled"]; [pool release]; } - (void) awakeFromNib { NSLog(@"MyAppController awake\n"); sInstance = self; [toWindow setNextResponder:self]; [NSApp setDelegate:self]; [self addWindowToDocument:toWindow]; } - (MyDocument *)document { if ( !toDocument ) { toDocument = [[MyDocument alloc] init]; } return toDocument; } - (NSUndoManager *)undoManager { // !!! WARNING: there are multiple NSUndoManager's in this App // Note: when an editable text field is in focus, // NSTextField will create // a separate undo manager for editing text while that field is in focus. // This means that hitting undo/redo while editing a text field will not go beyond the scope of that field. // This will return the global undo manager if the keyWindow was registered // via [self addWindowToDocument:]; // Windows which are NOT part of the document (such as preferences, popups, etc.), will // return their own undoManager, and undo will do nothing while those windows are in front. // You can't undo preferences window changes, so we don't want to surprise the user. NSUndoManager *undomgr = [[NSApp keyWindow] undoManager]; if ( undomgr ) { static bool sFirstTime = true; if ( sFirstTime ) { sFirstTime = false; [undomgr setLevelsOfUndo:1000]; // set some sane limit [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(beginUndo:) name:NSUndoManagerWillUndoChangeNotification object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(beginUndo:) name:NSUndoManagerWillRedoChangeNotification object:nil]; [toDocument registerForUndoGrouping]; // [[NSNotificationCenter defaultCenter] addObserver:self // selector:@selector(endUndo:) // name:NSUndoManagerDidUndoChangeNotification // object:nil]; // [[NSNotificationCenter defaultCenter] addObserver:self // selector:@selector(endUndo:) // name:NSUndoManagerDidRedoChangeNotification // object:nil]; } } return undomgr; } - (void) showStatusText: (id)iStatusText { ... implementation specific ... } - (void) beginUndo:(id)sender { // implementation specific stuff here NSUndoManager *undomgr = [[NSApp keyWindow] undoManager]; if ( [sender object] == undomgr ) { if ( [undomgr isUndoing] ) [self showStatusText: [NSString stringWithFormat:@"Undo %@", [undomgr undoActionName]]]; else if ( [undomgr isRedoing] ) [self showStatusText: [NSString stringWithFormat:@"Redo %@", [undomgr redoActionName]]]; } } // Add a window (with a window controller) to our document, so that the window // uses the document's NSUndoManager. In the future, we may want to use other features of NSDocument. - (void)addWindowToDocument:(NSWindow *)iWindow { NSString *autosaveName = [iWindow frameAutosaveName]; // preserve for "mainWindow", others. NSWindowController *winController = [iWindow windowController]; if ( !winController ) winController = [[NSWindowController alloc] initWithWindow:iWindow]; // create document if needed, and add window to document. [[self document] addWindowController: winController]; if ( autosaveName ) [iWindow setFrameAutosaveName:autosaveName]; // restore original for "mainWindow", others. [winController setNextResponder:self]; // keep last hotkey destination... see keyDown: } - (void) myOpenFile:(NSString*)path { // this is just a skeleton of what I do to track unsaved changes between relaunches [toDocument setFilePath:path]; ... implementation specific ... [[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithBool:NO] forKey:@"isDocumentEdited"]; [toDocument updateChangeCount:NSChangeCleared]; [[NSUserDefaults standardUserDefaults] setObject:[toDocument filePath] forKey:@"LastSaveFile"]; BOOL success = [[NSUserDefaults standardUserDefaults] synchronize]; // bootstrap // kpk very important... resetStandardUserDefaults forces the immutable // tree returned by dictionaryWithContentsOfFile to be mutable once re-read. // Apple: "Synchronizes any changes made to the shared user defaults object and releases it from memory. // A subsequent invocation of standardUserDefaults creates a new shared user defaults object with the standard search list." [NSUserDefaults resetStandardUserDefaults]; NSString *name = [[NSUserDefaults standardUserDefaults] objectForKey:@"LastSaveFile"]; } - (void) mySaveData:(NSString*)path { // this is just a skeleton of what I do to track unsaved changes between relaunches @try { ... implement something inherently dangerous... commit changes to a file ... if ( !errorStr ) { if ( [toDocument isDocumentEdited] ) { // UInt64 theTimeNow = VMPGlue::GetMilliS(); [[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithBool:NO] forKey:@"isDocumentEdited"]; [[NSUserDefaults standardUserDefaults] synchronize]; // bootstrap // DLog( @"synchronize success %d ms", (int)(VMPGlue::GetMilliS() - theTimeNow) ); } // tbd consider MyDocument saveToURL:ofType:forSaveOperation:error: [toDocument updateChangeCount:NSChangeCleared]; } @catch (...) { ... run critical alert ... } } - (void) finishLoadingData { @try { if ( dataexists ) { ... implement something inherently dangerous... loading your data from a file [toDocument setFilePath: [[NSUserDefaults standardUserDefaults] objectForKey:@"LastSaveFile"]]; NSNumber *num = [[NSUserDefaults standardUserDefaults] objectForKey:@"isDocumentEdited"]; if ( [num boolValue] == YES ) [toDocument updateChangeCount:NSChangeDone]; } else { [[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithBool:NO] forKey:@"isDocumentEdited"]; [toDocument updateChangeCount:NSChangeCleared]; } sFinishedLaunching |= kFinishedLoadingData; } @catch (...) { // !!! will not return !!! ... run critical alert ... // !!! will not return !!! } } #pragma mark NSApplication delegate // Apple: Sent directly by theApplication to the delegate. The method should open the file filename, //returning YES if the file is successfully opened, and NO otherwise. //If the user started up the application by double-clicking a file, the delegate receives the application:openFile: message before receiving applicationDidFinishLaunching:. //(applicationWillFinishLaunching: is sent before application:openFile:.) - (BOOL)application:(NSApplication *)sender openFile:(NSString *)filename { BOOL didOpen = [MyDocument openMyDocument: filename]; sFinishedLaunching |= kFinishedOpenFile; return didOpen; } // NSApplication notification - (void) applicationDidFinishLaunching:(NSNotification*)note { // kpk note: currentEvent is often nil at this point! [[NSApp currentEvent] modifierFlags] CGEventFlags modifierFlags = CGEventSourceFlagsState(kCGEventSourceStateHIDSystemState); sFinishedLaunching |= kFinishedWaking; if ( modifierFlags &amp; (kCGEventFlagMaskShift | kCGEventFlagMaskCommand) ) { ... implementation specific ... alert: @"Shift or Command key held down at startup.\nWhat would you like to do?" title: @"Startup Options" canContinue: @"Continue" ]; } sFinishedLaunching |= kFinishedPreLaunchCheck; [self finishLoadingData]; sFinishedLaunching |= kFinishedAndReadyToDraw; } - (BOOL)windowShouldClose:(id)sender { if ( [sender isKindOfClass: [NSWindow class]] &amp;&amp; sender != toWindow ) return YES; // allow non-document-edit windows to close normally ... in my implementation, I prompt user with save/quit options when edit window is closed ... return NO; } - (NSApplicationTerminateReply) applicationShouldTerminate:(NSApplication*)sender { if ( !gWantsToQuit &amp;&amp; [toDocument isDocumentEdited] ) { if ( ![self windowShouldClose:self] ) return NSTerminateCancel; } return NSTerminateNow; } - (void) applicationWillTerminate:(NSNotification *)notification { if ( gWantsToQuit ) { ... implementation specific ... dont save potentially wonky data if relaunch is required } else { [self saveData: [toDocument filePath]]; } } @end </code></pre>
 

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