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  • ObjC get property name

    - by Joe Even
    Yes. I've searched a lot without success. I've looking for a way to get a property name as StringValue from inside a method. Lets say: My class has X Subviews from the Type UILabel. @property (strong, nonatomic) UILabel *firstLabel; @property (strong, nonatomic) UILabel *secondLabel; [...] and so on. Inside the method foo, the views are iterated as followed: -(void) foo { for (UIView *view in self.subviews) { if( [view isKindOfClass:[UILabel class]] ) { /* codeblock that gets the property name. */ } } } The Result should be something like that: THE propertyName(NSString) OF view(UILabel) IS "firstLabel" I've tried class_getInstanceVariable, object_getIvar and property_getName without Success. For Example, the Code for: [...] property_getName((void*)&view) [...] RETURNS: <UILabel: 0x6b768c0; frame = (65 375; 219 21); text = 'Something'; clipsToBounds = YES; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <CALayer: 0x6b76930>> But i'm looking for this kind of result: "firstLabel" , "secondLabel" and so on. Thanks for your help! Reagrds Joé

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  • I want to support UIInterfaceOrientationLandscapeRight and UIInterfaceOrientationLandscapeLeft only

    - by orangecl4now
    how do I make sure that UIInterfaceOrientationPortraitRight and UIInterfaceOrientationPortraitLeft are not supported. Basically I want my application to be used ONLY in UIInterfaceOrientationLandscapeRight and UIInterfaceOrientationLandscapeLeft I edited the Info.plist file MainWindow UISupportedInterfaceOrientations UIInterfaceOrientationLandscapeLeft UIInterfaceOrientationLandscapeRight

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  • Loading contents of TableView Controller after showing Tab

    - by Teo
    Hello, I have a 4 tabbar application. The second tab has a tableviewController. When i select the second tab the tableview is displayed with it's contents and it works fine. The problem is that that data is comming from the network and it talks 2-3 seconds to load. So when i press the second tab it goes there after the contents have been loaded. How can i show an empty tableview (i'll put an activity indicator) and then load and show the contents? Teo

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  • Attributed strings in UITableViewCells without WebView?

    - by arnekolja
    Hello, does anyone know if there's a way in with 3.0+ to display attributed strings within a UITableViewCell without using a UIWebView for that? I need to display a string with linked, tappable substrings as the typical detailTextLabel. I wouldn't mind exchanging this UILabel against another type of view, but I think a UIWebView could be just too slow when rendering a table with hundrets of cells. Or does someone have opposite experiences here? So my question is: what's the best way to achieve mixed strings in a very large table without a great performance hit? I searched for this almost a whole day now, but I can only find old posts mentioning that there's no attributed string on the iPhone (outdated, as this was pre-3.0) and/or saying that they use a UIWebView for that. But really, I don't think this would perform very well on large tables, would it? Many, many thanks in advance Arne

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  • How can I conditionally color files and folders in the OS X Finder?

    - by Girish Kolari
    I want to color badge files and folders based on the some condition in finder, what is the approach to achieve this in Mac OS X 10.6 I have checked this question: This only talk about the context menu in finder http://stackoverflow.com/questions/1651075/finder-plugin-in-snow-leopard I have even checked: http://scplugin.tigris.org/ even they don't do color badging in 10.6 which is pending task. Thanks in advance for your all help

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  • Using Singleton synchronized array with NSThread

    - by hmthur
    I have a books app with a UISearchBar, where the user types any book name and gets search results (from ext API call) below as he types. I am using a singleton variable in my app called retrievedArray which stores all the books. @interface Shared : NSObject { NSMutableArray *books; } @property (nonatomic, retain) NSMutableArray *books; + (id)sharedManager; @end This is accessed in multiple .m files using NSMutableArray *retrievedArray; ...in the header file retrievedArray = [[Shared sharedManager] books]; My question is how do I ensure that the values inside retrievedArray remain synchronized across all the classes. Actually the values inside retrievedArray gets added through an NSXMLParser (i.e. through external web service API). There is a separate XMLParser.m file, where I do all the parsing and fill the array. The parsing is done on a separate thread. - (void) run: (id) param { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL: [self URL]]; [parser setDelegate: self]; [parser parse]; [parser release]; NSString *tmpURLStr = [[self URL]absoluteString]; NSRange range_srch_book = [tmpURLStr rangeOfString:@"v1/books"]; if (range_srch_book.location != NSNotFound) [delegate performSelectorOnMainThread:@selector(parseDidComplete_srch_book) withObject:nil waitUntilDone:YES]; [pool release]; } - (void) parseXMLFile: (NSURL *) url { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; [self setURL: url]; NSThread* myThread = [[NSThread alloc] initWithTarget:self selector:@selector(run:) object: nil]; [retrievedArray removeAllObjects]; [myThread start]; [pool release]; } There seems to be some synchronization issues if the user types very quickly (It seems to be working fine if the user types slowly)....So there are 2 views in which the content of an object in this shared array item is displayed; List and Detail. If user types fast and clicks on A in List view, he is shown B in detail view...That is the main issue. I have tried literally all the solutions I could think of, but am still unable to fix the issue. Please suggest some suitable fixes.

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  • Convert NSData into Hex NSString

    - by Dawson
    With reference to the following question: Convert NSData into HEX NSSString I have solved the problem using the solution provided by Erik Aigner which is: NSData *data = ...; NSUInteger capacity = [data length] * 2; NSMutableString *stringBuffer = [NSMutableString stringWithCapacity:capacity]; const unsigned char *dataBuffer = [data bytes]; NSInteger i; for (i=0; i<[data length]; ++i) { [stringBuffer appendFormat:@"%02X", (NSUInteger)dataBuffer[i]]; } However, there is one small problem in that if there are extra zeros at the back, the string value would be different. For eg. if the hexa data is of a string @"3700000000000000", when converted using a scanner to integer: unsigned result = 0; NSScanner *scanner = [NSScanner scannerWithString:stringBuffer]; [scanner scanHexInt:&result]; NSLog(@"INTEGER: %u",result); The result would be 4294967295, which is incorrect. Shouldn't it be 55 as only the hexa 37 is taken? So how do I get rid of the zeros? EDIT: (In response to CRD) Hi, thanks for clarifying my doubts. So what you're doing is to actually read the 64-bit integer directly from a byte pointer right? However I have another question. How do you actually cast NSData to a byte pointer? To make it easier for you to understand, I'll explain what I did originally. Firstly, what I did was to display the data of the file which I have (data is in hexadecimal) NSData *file = [NSData dataWithContentsOfFile:@"file path here"]; NSLog(@"Patch File: %@",file); Output: Next, what I did was to read and offset the first 8 bytes of the file and convert them into a string. // 0-8 bytes [file seekToFileOffset:0]; NSData *b = [file readDataOfLength:8]; NSUInteger capacity = [b length] * 2; NSMutableString *stringBuffer = [NSMutableString stringWithCapacity:capacity]; const unsigned char *dataBuffer = [b bytes]; NSInteger i; for (i=0; i<[b length]; ++i) { [stringBuffer appendFormat:@"%02X", (NSUInteger)dataBuffer[i]]; } NSLog(@"0-8 bytes HEXADECIMAL: %@",stringBuffer); As you can see, 0x3700000000000000 is the next 8 bytes. The only changes I would have to make to access the next 8 bytes would be to change the value of SeekFileToOffset to 8, so as to access the next 8 bytes of data. All in all, the solution you gave me is useful, however it would not be practical to enter the hexadecimal values manually. If formatting the bytes as a string and then parsing them is not the way to do it, then how do I access the first 8 bytes of the data directly and cast them into a byte pointer?

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  • NSNotification postNotificationName in AppDelegate but NSNotificationCenter in ViewController?

    - by James Testa
    I can't get the selector method, receiveChatText, in the NSNotificationCenter to execute and I am wondering if the problem is because the NSNotification postNotificationName is in AppDelegate.m but NSNotificationCenter is in ViewController.m? I.E. can the postNotificationName know that the NSNotificationCenter is in another viewController file or is that something I need to tell it? In a viewController.m I have -(id)init { self = [super init]; if(self){ [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveChatText:) name:ChatMessageReceived object:nil]; return self; } - (void)receiveChatText:(NSNotification *)note { NSLog(@"received chat text"); } and in the top level AppDelegate.m file I have the following: -(void) didReceiveMessage { [[NSNotificationCenter defaultCenter] postNotificationName:ChatMessageReceived object:nil userInfo:nil]; } Any ideas what could stop receiveChatText from being executed when didReceiveMessage is called?

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  • Can NSTask safely be used outside the main thread?

    - by neoneye
    Yesterday I read somewhere that NSTask isn't thread safe and that bothers me a lot, because I'm running a NSTask within a NSThread and is so far not experiencing any threading issues with it. My code is organized like this A: main thread -> B: worker thread -> C: worker task C: The worker task is a commandline program. B: The worker thread can start/stop the worker task and send it commands. A: The main thread can send commands to the worker thread. If NSTask is supposed to be used only within the main thread, then I'm considering moving the NSTask start/stop code to the main thread, just to prevent possible threading issues. Can NSTask be used outside the main thread? And if not then what may be the threading issues with NSTask?

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  • Casting to specify unknown object type?

    - by fuzzygoat
    In the following code I have a view object that is an instance of UIScrollView, if I run the code below I get warnings saying that "UIView might not respond to -setContentSize etc." UIImage *image = [UIImage imageNamed:@"Snowy_UK.jpg"]; imageView = [[UIImageView alloc] initWithImage:image]; [[self view] addSubview:imageView]; [[self view] setContentSize:[image size]]; [[self view] setMaximumZoomScale:2.0]; [[self view] setMinimumZoomScale: [[self view] bounds].size.width / [image size].width]; I have checked the type of the object and [self view] is indeed a UIScrollView. I am guessing that this is just the compiler making a bad guess as to the type and the solution is simply to cast the object to the correct type manually, am I getting this right? UIScrollView *scrollView = (UIScrollView *)[self view]; UIImage *image = [UIImage imageNamed:@"Snowy_UK.jpg"]; imageView = [[UIImageView alloc] initWithImage:image]; [[self view] addSubview:imageView]; [scrollView setContentSize:[image size]]; [scrollView setMaximumZoomScale:2.0]; [scrollView setMinimumZoomScale: [scrollView bounds].size.width / [image size].width]; cheers Gary.

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  • Gradual memory leak in loop over contents of QTMovie

    - by Benji XVI
    I have a simple foundation tool that exports every frame of a movie as a .tiff file. Here is the relevant code: NSString* movieLoc = [NSString stringWithCString:argv[1]]; QTMovie *sourceMovie = [QTMovie movieWithFile:movieLoc error:nil]; int i=0; while (QTTimeCompare([sourceMovie currentTime], [sourceMovie duration]) != NSOrderedSame) { // save image of movie to disk NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSData *currentImageData = [[sourceMovie currentFrameImage] TIFFRepresentation]; [currentImageData writeToFile:filePath atomically:NO]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } [pool drain]; return 0; As you can see, in order to prevent very large memory buildups with the various transparently-autoreleased variables in the loop, we create, and flush, an autoreleasepool with every run through the loop. However, over the course of stepping through a movie, the amount of memory used by the program still gradually increases. Instruments is not detecting any memory leaks per se, but the object trace shows certain General Data blocks to be increasing in size. [Edited out reference to slowdown as it doesn't seem to be as much of a problem as I thought.] Edit: let's knock out some parts of the code inside the loop & see what we find out... Test 1 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } Here we simply loop over the whole movie, creating the filename and logging it. Memory characteristics: remains at 15MB usage for the duration. Test 2 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; [sourceMovie stepForward]; [arp release]; } Here we add back in the creation of the NSImage from the current frame. Memory characteristics: gradually increasing memory usage. RSIZE is at 60MB by frame 200; 75MB by f300. Test 3 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; NSData *imageData = [image TIFFRepresentation]; [sourceMovie stepForward]; [arp release]; } We've added back in the creation of an NSData object from the NSImage. Memory characteristics: Memory usage is again increasing: 62MB at f200; 75MB at f300. In other words, largely identical. It looks like a memory leak in the underlying system QTMovie uses to do currentFrameImage, to me.

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  • I can't use dashes in XPATH on iphone using libxml2

    - by user249488
    I'm trying to parse HTML data using KissXML for iphone. I've noticed that I can't have dashes in the id() tag, otherwise it won't evaluate. For example, if I'm trying to get the element at I would do id("foo") However, if I try to get at element , and I try id("foo-bar") the libxml2 XPATH engine doesn't seem to return anything. It works using the XPATH check for firefox, though. Anyone run into this issue and know of a reason why it's happening or have a workaround (besides using the absolute XPATH path?)

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  • How to load a NIB inside of a view in another NIB?

    - by Sheehan Alam
    I have two NIB's ParentViewController.xib ChildViewController.xib ParentViewController.xib contains a UIView and a UIViewController. ChildViewController.xib contains a UIButton I want ChildViewController.xib to load in the ParentViewController.xib's UIView I have done the following: Created @property for UIView in ParentViewController Connected File's Owner to UIView in ParentViewController Set UIViewController in ParentViewController's NIB Name property to ChildViewController in Interface Builder Set ChildViewController view property to UIView in ParentViewController I was hoping this would load ChildViewController into my UIView in ParentViewController but no luck. I did get the following warning, which could be the culprit: 'View Controller (Child View)' has both its 'NIB Name' property set and its 'view' outlet connected. This configuration is not supported. I also have added additional code in ParentViewController's viewDidLoad(): - (void)viewDidLoad { [super viewDidLoad]; ChildViewController *childViewController = [[ChildViewController alloc]initWithNibName:@"ChildViewController" bundle:nil]; childViewController.view = self.myView; } Any thoughts on why ChildViewController does not load in the UIView of ParentViewController?

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  • Comparing an [NSURL path] to an NSString doesn't work

    - by Koning Baard XIV
    I have this code: NSLog([url path]); if([url path] == @"/connect/login_success.html") { NSLog("IT WORKZ"); } When I run my application, do the login etc... my console says: 2010-05-04 23:49:57.297 Framebook Test Application[8069:a0f] /connect/login_success.html But it should also print IT WORKZ to the console, which it does not. Can anyone help me? Thanks.

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  • App is crashing as soon as UITableView gets reloaded

    - by OhhMee
    Hello, I'm developing an app where TableView needs to reload as soon as the login process gets completed. The app crashes with error EXC_BAD_ACCESS when the table data gets reloaded. It doesn't crash when I remove all case instances except case 0: What could be the reason behind it? Here's the code: - (void)viewDidLoad { [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(loginDone:) name:@"loginDone" object:nil]; statTableView.backgroundColor = [UIColor clearColor]; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger) section { return 6; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; } // Configure the cell. switch (indexPath.row) { case 0 : cell.textLabel.text = @"Foo:"; NSLog(@"%@", data7); UILabel *myLabel2 = [[UILabel alloc] initWithFrame:CGRectMake(200, 10, 20, 30)]; myLabel2.text = (@"%@", data7); myLabel2.textColor = [UIColor blackColor]; myLabel2.backgroundColor = [UIColor whiteColor]; myLabel2.font = [UIFont fontWithName:@"Trebuchet MS" size:14]; [cell.contentView addSubview:myLabel2]; break; case 1: cell.textLabel.text = @"Foo: "; UILabel *myLabel4 = [[UILabel alloc] initWithFrame:CGRectMake(200, 10, 20, 30)]; myLabel4.text = (@"%@", data11); myLabel4.textColor = [UIColor blackColor]; myLabel4.backgroundColor = [UIColor whiteColor]; myLabel4.font = [UIFont fontWithName:@"Trebuchet MS" size:14]; [cell.contentView addSubview:myLabel4]; break; case 2: cell.textLabel.text = @"Foo: "; UILabel *myLabel8 = [[UILabel alloc] initWithFrame:CGRectMake(200, 10, 20, 30)]; myLabel8.text = (@"%@", data3); myLabel8.textColor = [UIColor blackColor]; myLabel8.backgroundColor = [UIColor whiteColor]; myLabel8.font = [UIFont fontWithName:@"Trebuchet MS" size:14]; [cell.contentView addSubview:myLabel8]; break; case 3: cell.textLabel.text = @"Foo: "; UILabel *myLabel10 = [[UILabel alloc] initWithFrame:CGRectMake(200, 10, 20, 30)]; myLabel10.text = [NSString stringWithFormat:@"%@", data4]; if ([data4 isEqualToString:@"0"]) { myLabel10.text = @"None"; } myLabel10.textColor = [UIColor blackColor]; myLabel10.backgroundColor = [UIColor whiteColor]; myLabel10.font = [UIFont fontWithName:@"Trebuchet MS" size:14]; [cell.contentView addSubview:myLabel10]; break; case 4: cell.textLabel.text = @"Foo: "; UILabel *myLabel12 = [[UILabel alloc] initWithFrame:CGRectMake(200, 10, 20, 30)]; myLabel12.text = [NSString stringWithFormat:@"%@", data5]; myLabel12.textColor = [UIColor blackColor]; if ([data5 isEqualToString:@"Foo"]) { myLabel12.textColor = [UIColor redColor]; myLabel12.text = @"Nil"; } myLabel12.backgroundColor = [UIColor whiteColor]; myLabel12.font = [UIFont fontWithName:@"Trebuchet MS" size:14]; [cell.contentView addSubview:myLabel12]; break; case 5: cell.textLabel.text = @"Foo: "; UILabel *myLabel14 = [[UILabel alloc] initWithFrame:CGRectMake(200, 10, 50, 30)]; if ([data6 isEqualToString:@"Foo"]) { myLabel14.textColor = [UIColor colorWithRed:(0/255.f) green:(100/255.f) blue:(0/255.f) alpha:1.0]; myLabel14.text = @"No Dues"; } else { myLabel14.text = [NSString stringWithFormat:@"%@", data6]; myLabel14.textColor = [UIColor redColor]; } myLabel14.backgroundColor = [UIColor whiteColor]; myLabel14.font = [UIFont fontWithName:@"Trebuchet MS" size:14]; [cell.contentView addSubview:myLabel14]; break; /* [myLabel2 release]; [myLabel4 release]; [myLabel8 release]; [myLabel10 release]; [myLabel12 release]; [myLabel14 release]; */ } return cell; }

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  • Cancel a UIView animation?

    - by Phil Nash
    Is it possible to cancel a UIView animation while it is in progress? Or would I have to drop to the CA level? i.e. I've done something like this (maybe setting an end animation action too): [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:duration]; [UIView setAnimationCurve: UIViewAnimationCurveLinear]; // other animation properties // set view properties [UIView commitAnimations]; But before the animation completes and I get the animation ended event, I want to cancel it (cut it short). Is this possible? Googling around finds a few people asking the same question with no answers - and one or two people speculating that it can't be done.

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  • After I apply custom logic, next UI action crashes my app.

    - by DanF
    I've got an team (eveningRoster) that I'm making a button add employees to. The team is really a relationship to that night's event, but it's represented with an AC. I wanted to make sure an employee did not belong to the team before it adds, so I added a method to MyDocument to check first. It seems to work, the error logs complete, but after I've added a member, the next time I click anything, the program crashes. Any guesses why? Here's the code: -(IBAction)playsTonight:(id)sender { NSArray *selection = [fullRoster selectedObjects]; NSArray *existing = [eveningRoster arrangedObjects]; //Result will be within each loop. BOOL result; //noDuplicates will stay YES until a duplicate is found. BOOL noDuplicates = YES; //For the loop: int count; for (count = 0; count < [selection count]; count++){ result = [existing containsObject:[selection objectAtIndex:count]]; if (result == YES){ NSLog(@"Duplicate found!"); noDuplicates = NO; } } if (noDuplicates == YES){ [eveningRoster addObjects:[fullRoster selectedObjects]]; NSLog(@"selected objects added."); [eveningTable reloadData]; NSLog(@"Table reloaded."); } [selection release]; [existing release]; return; }

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  • Accepting drag operations in an NSCollectionView subclass

    - by andyvn22
    I've subclassed NSCollectionView and I'm trying to receive dragged files from the Finder. I'm receiving draggingEntered: and returning an appropriate value, but I'm never receiving prepareForDragOperation: (nor any of the methods after that in the process). Is there something obvious I'm missing here? Code: - (void)awakeFromNib { [self registerForDraggedTypes:[NSArray arrayWithObjects:NSFilenamesPboardType, nil]]; } - (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender { NSLog(@"entered"); //Happens NSPasteboard *pboard; NSDragOperation sourceDragMask; sourceDragMask = [sender draggingSourceOperationMask]; pboard = [sender draggingPasteboard]; if ([[pboard types] containsObject:NSFilenamesPboardType]) { NSLog(@"copy"); //Happens return NSDragOperationCopy; } return NSDragOperationNone; } - (BOOL)prepareForDragOperation:(id <NSDraggingInfo>)sender { NSLog(@"prepare"); //Never happens return YES; }

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  • In iPhone OS, what UTI represents a plain ol' text file?

    - by Justin Searls
    I'm attempting to make use of the UIDocumentInteractionController mechanism in iPhone OS 3.2, but I'm struggling to figure out exactly how to construct a UTI that it likes. I've gotten as far as attempting to set "public.plain-text", but it's hard to test whether this is the correct UTI for a plain text document, since I can't tell whether the issue is that my iPad doesn't have any apps that support plain text import. (I figured Pages would, but I suppose perhaps not, since it will attempt and fail to load any files with the extension .pages, regardless of UTI). Any seasoned OS X developers that can help on this?

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  • UITableView Animation when entering Editmode

    - by f0rz
    Hi! Maybe I´m just stupid but I cant understand why this isnt working. I want to achieve a little animation when I'm entering editing mode within a UITableView. [super setEditing:NO animated:YES]; [myTable setEditing:NO animated:YES]; [myTable reloadData]; [self.navigationItem.leftBarButtonItem setTitle:@"Edit"]; [self.navigationItem.leftBarButtonItem setStyle:UIBarButtonItemStylePlain]; Shouldnt this animated:YES suppose to animated this entering of the editmode? Regards. - f0rz

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  • Strategy to keep track of stored files in the documents directory?

    - by mystify
    In my app, the user can save his input to disk. This is done with NSKeyedArchiver. Currently I simply name my files with a timestamp. But of course, the user may want to load one of them back in to keep on editing them. What would be the most reliable / safe strategy to keep track of those files? I need to present the user a list of those files, so that he can choose one to open. Currently I think of making an archived NSMutableArray which simply stores the file names, but I feel that this strategy is not really good. We all know when we save files sometimes something goes wrong, and this seems very likely to get currupted easily, or not? How would you do it?

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  • Setting up a "to-many" relationship value dependency for a transient Core Data attribute

    - by Greg Combs
    I've got a relatively complicated Core Data relationship structure and I'm trying to figure out how to set up value dependencies (or observations) across various to-many relationships. Let me start out with some basic info. I've got a classroom with students, assignments, and grades (students X assignments). For simplicity's sake, we don't really have to focus much on the assignments yet. StudentObj <--->> ScoreObj <<---> AssignmentObj Each ScoreObj has a to-one relation with the StudentObj and the AssignmentObj. ScoreObj has real attributes for the numerical grade, the turnInDate, and notes. AssignmentObj.scores is the set of Score objects for that assignment (N = all students). AssignmentObj has real attributes for name, dueDate, curveFunction, gradeWeight, and maxPoints. StudentObj.scores is the set of Score objects for that student (N = all assignments). StudentObj also has real attributes like name, studentID, email, etc. StudentObj has a transient (calculated, not stored) attribute called gradeTotal. This last item, gradeTotal, is the real pickle. it calculates the student's overall semester grade using the scores (ScoreObj) from all their assignments, their associated assignment gradeWeights, curves, and maxPoints, and various other things. This gradeTotal value is displayed in a table column, along with all the students and their individual assignment grades. Determining the value of gradeTotal is a relatively expensive operation, particularly with a large class, therefore I want to run it only when necessary. For simplicity's sake, I'm not storing that gradeTotal value in the core data model. I don't mind caching it somewhere, but I'm having a bitch of a time determining where and how to best update that cache. I need to run that calculation for each student whenever any value changes that affects their gradeTotal. If this were a simple to-one relationship, I know I could use something like keyPathsForValuesAffectingGradeTotal ... but it's more like a many-to-one-to-many relationship. Does anyone know of an elegant (and KVC correct) solution? I guess I could tear through all those score and assignment objects and tell them to register their students as observers. But this seems like a blunt force approach.

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