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  • should variable be retained or not? iphone-sdk

    - by psebos
    Hi, in the following piece of code I got from a book. The NSString *pPath which is defined in the class as an instance variable. @interface MainViewController : UIViewController { NSString *pPath; } In the implementation after being set it is being retained. I assume that with the assignment the object is automatically retained (because it is an NSString) and there is no need to additionally retain it. - (void) initPrefsFilePath { NSString *documentsDirectory = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"]; pPath = [documentsDirectory stringByAppendingPathComponent: @"flippingprefs.plist"]; [pPath retain]; }

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  • Can't get Jacobi algorithm to work in Objective-C

    - by Chris Long
    Hi, For some reason, I can't get this program to work. I've had other CS majors look at it and they can't figure it out either. This program performs the Jacobi algorithm (you can see step-by-step instructions and a MATLAB implementation here). BTW, it's different from the Wikipedia article of the same name. Since NSArray is one-dimensional, I added a method that makes it act like a two-dimensional C array. After running the Jacobi algorithm many times, the diagonal entries in the NSArray (i[0][0], i[1][1], etc.) are supposed to get bigger and the others approach 0. For some reason though, they all increase exponentially. For instance, i[2][4] should equal 0.0000009, not 9999999, while i[2][2] should be big. Thanks in advance, Chris NSArray+Matrix.m @implementation NSArray (Matrix) @dynamic offValue, transposed; - (double)offValue { double sum = 0.0; for ( MatrixItem *item in self ) if ( item.nonDiagonal ) sum += pow( item.value, 2.0 ); return sum; } - (NSMutableArray *)transposed { NSMutableArray *transpose = [[[NSMutableArray alloc] init] autorelease]; int i, j; for ( i = 0; i < 5; i++ ) { for ( j = 0; j < 5; j++ ) { [transpose addObject:[self objectAtRow:j andColumn:i]]; } } return transpose; } - (id)objectAtRow:(NSUInteger)row andColumn:(NSUInteger)column { NSUInteger index = 5 * row + column; return [self objectAtIndex:index]; } - (NSMutableArray *)multiplyWithMatrix:(NSArray *)array { NSMutableArray *result = [[NSMutableArray alloc] init]; int i = 0, j = 0, k = 0; double value; for ( i = 0; i < 5; i++ ) { value = 0.0; for ( j = 0; j < 5; j++ ) { for ( k = 0; k < 5; k++ ) { MatrixItem *firstItem = [self objectAtRow:i andColumn:k]; MatrixItem *secondItem = [array objectAtRow:k andColumn:j]; value += firstItem.value * secondItem.value; } MatrixItem *item = [[MatrixItem alloc] initWithValue:value]; item.row = i; item.column = j; [result addObject:item]; } } return result; } @end Jacobi_AlgorithmAppDelegate.m // ... - (void)jacobiAlgorithmWithEntry:(MatrixItem *)entry { MatrixItem *b11 = [matrix objectAtRow:entry.row andColumn:entry.row]; MatrixItem *b22 = [matrix objectAtRow:entry.column andColumn:entry.column]; double muPlus = ( b22.value + b11.value ) / 2.0; muPlus += sqrt( pow((b22.value - b11.value), 2.0) + 4.0 * pow(entry.value, 2.0) ); Vector *u1 = [[[Vector alloc] initWithX:(-1.0 * entry.value) andY:(b11.value - muPlus)] autorelease]; [u1 normalize]; Vector *u2 = [[[Vector alloc] initWithX:-u1.y andY:u1.x] autorelease]; NSMutableArray *g = [[[NSMutableArray alloc] init] autorelease]; for ( int i = 0; i <= 24; i++ ) { MatrixItem *item = [[[MatrixItem alloc] init] autorelease]; if ( i == 6*entry.row ) item.value = u1.x; else if ( i == 6*entry.column ) item.value = u2.y; else if ( i == ( 5*entry.row + entry.column ) || i == ( 5*entry.column + entry.row ) ) item.value = u1.y; else if ( i % 6 == 0 ) item.value = 1.0; else item.value = 0.0; [g addObject:item]; } NSMutableArray *firstResult = [[g.transposed multiplyWithMatrix:matrix] autorelease]; matrix = [firstResult multiplyWithMatrix:g]; } // ...

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  • Nested functions not allowed in drawrect problem

    - by Martin
    I have a custom view onto which I draw some graphics from the drawrect function, which works fine. However I like to draw based on the contens of an array I pass on the the view just before I do a setNeedsDisplay. In the drawRect function I try to access the array but then I get a nested functions error which I do not understand. Here's my code: // // MyView.h // window // #import <UIKit/UIKit.h> @interface MyView : UIView { NSArray * nary; } @property (nonatomic, copy) NSArray *nary; @end // // MyView.m // window // #import "MyView.h" @implementation MyView @synthesize nary; CGContextRef c; CGFloat black[4] = {0.0f, 0.0f, 0.0f, 1.0f}; - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { // Initialization code } return self; } - (void)drawRect:(CGRect)rect { c = UIGraphicsGetCurrentContext(); CGContextSetStrokeColor(c, black); NSLog(@"mview"); NSArray *ns = [nary objectAtIndex:0]; } - (void)dealloc { [super dealloc]; } @end

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  • If my application doesn't use a lot of memory, can I ignore viewDidUnload:?

    - by iPhoneToucher
    My iPhone app generally uses under 5MB of living memory and even in the most extreme conditions stays under 8MB. The iPhone 2G has 128MB of RAM and from what I've read an app should only expect to have 20-30MB to use. Given that I never expect to get anywhere near the memory limit, do I need to care about memory warnings and setting objects to nil in viewDidUnload:? The only way I see my app getting memory warnings is if something else on the phone is screwing with the memory, in which case the entire phone would be acting silly. I built my app without ever using viewDidUnload:, so there's more than a hundred classes that I'd need to inspect and add code to if I did need to implement it.

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  • How do I break down an NSTimeInterval into year, months, days, hours, minutes and seconds on iPhone?

    - by willc2
    I have a time interval that spans years and I want all the time components from year down to seconds. My first thought is to integer divide the time interval by seconds in a year, subtract that from a running total of seconds, divide that by seconds in a month, subtract that from the running total and so on. That just seems convoluted and I've read that whenever you are doing something that looks convoluted, there is probably a built-in method. Is there? I integrated Alex's 2nd method into my code. It's in a method called by a UIDatePicker in my interface. NSDate *now = [NSDate date]; NSDate *then = self.datePicker.date; NSTimeInterval howLong = [now timeIntervalSinceDate:then]; NSDate *date = [NSDate dateWithTimeIntervalSince1970:howLong]; NSString *dateStr = [date description]; const char *dateStrPtr = [dateStr UTF8String]; int year, month, day, hour, minute, sec; sscanf(dateStrPtr, "%d-%d-%d %d:%d:%d", &year, &month, &day, &hour, &minute, &sec); year -= 1970; NSLog(@"%d years\n%d months\n%d days\n%d hours\n%d minutes\n%d seconds", year, month, day, hour, minute, sec); When I set the date picker to a date 1 year and 1 day in the past, I get: 1 years 1 months 1 days 16 hours 0 minutes 20 seconds which is 1 month and 16 hours off. If I set the date picker to 1 day in the past, I am off by the same amount. Update: I have an app that calculates your age in years, given your birthday (set from a UIDatePicker), yet it was often off. This proves there was an inaccuracy, but I can't figure out where it comes from, can you?

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  • Blur CALayer's Superlayer

    - by eaigner
    Hi. I've got a CALayer and a sublayer in it. What i want to achieve is a blur of the superlayer (the area under the sublayer), just like the standard sheets do it. I've tried to set a .compositingFilter on the sublayer but this doesn't seem to work. Any ideas how to solve this?

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  • method returning wrong variable

    - by cocoanewbie
    This class I'm working with has three instance variables I'm interested in, NSmutablearrays xArray yArray and zArray, there are also other NSmutablearrays, a, bArray and c. I just added accessors - (NSMutableArray *) xArray { return xArray; } ditto for y and z. However, it's returning yArray, zArray and bArray for some reason. Why is that happening? Okay, I just changed the names of the methods to GetXArray and everything seems to be returning the right variables. Now I'm really confused. How the heck did this happen and how do I prevent this from happening in the future?

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  • ios how can user cancel facebook sign in?

    - by Jackson
    When a user gets to this screen, there is no way to cancel out of it. What can I do? To get this view in the first place I am running: NSMutableDictionary *params = [NSMutableDictionary dictionaryWithObjectsAndKeys: vid, @"link", vid, @"source", vid, @"picture", @"My Place", @"name", @"YouTube Presentation", @"caption", title, @"description", @"Enjoy this Video", @"message", nil]; [app.facebook dialog:@"stream.publish" andParams:params andDelegate:self];

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  • Storing data locally and synchronizing it with data base on linux server

    - by Miraaj
    Hi all, I have developed a mac application, which is continuously interacting with database on linux server. As data is increasing it has become costlier affair in terms of time to fetch data from server. So I am planning to store required data locally, say on mysqlite and find some mechanism through which I can synchronize it with database on linux server. Can anyone suggest me some way to accomplish it? Thanks, Miraaj

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  • How do I make a UIAlertView happen only on the first start-up of an iPhone app?

    - by user309245
    I'm using the UIAlertView to make a pop-up happen once the app has started up. It works fine but I only want the pop up to happen on the first start-up of the app. At the moment I've got the UIAlertView in the AppDelegate class, after the application didFinishLaunching. Here is my code at the moment. - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { sleep(4); UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Welcome!" message:@"SAMPLE!!!" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; [alert release]; I'm new to app development so sorry if this is simple. Thanks in advance! :)

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  • get data from online once and then viewable offline

    - by user313100
    Okay, I want to have an app that takes phone numbers from an online database and displays them in a table view. When the user is not online, I want them to still be able to see the numbers they already got from the database in the table view. If the user manages to go back online, the database updates the view. My question is, is this possible to do and if so, what's the best way to approach it? (bit of a newbie, please help me out)

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  • simple CATextLayer scaling problem

    - by dersubtile
    I'm having a simple scaling problem with CATextLayer, but i just couldn't figure it out: I want the CATextLayer to proportionally grow in size with it's superlayer: if the superlayer's width is 300 the text size of CATextLayer should be 12 and if the supeview's width is 600 the text size should be 24. I couldn't find a working solution! Can you please give me a clue? Thanks, Julian.

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  • Retrieving a unique result set with Core Data

    - by randombits
    I have a core data based app that manages a bunch of entities. I'm looking to be able to do the following. I have an entity "SomeEntity" with the attributes: name, type, rank, foo1, foo2. Now, SomeEntity has several rows if when we're speaking strictly in SQL terms. What I'm trying to accomplish is to retrieve only available types, even though each instance can have duplicate types. I also need them returned in order according to rank. So in SQL, what I'm looking for is the following: SELECT DISTINCT(type) ORDER BY rank ASC Here is the code I have so far that's breaking: NSError *error = NULL; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; [fetchRequest setReturnsDistinctResults:YES]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"type", @"rank", nil]]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"SomeEntity" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; // sort by rank NSSortDescriptor *rankDescriptor = [[NSSortDescriptor alloc] initWithKey:@"rank" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:rankDescriptor,nil]; [fetchRequest setSortDescriptors:sortDescriptors]; [sortDescriptors release]; [rankDescriptor release]; NSArray *fetchResults = [managedObjectContext executeFetchRequest:fetchRequest error:&error]; [fetchRequest release]; return fetchResults; Right now that is crashing with the following: Invalid keypath section passed to setPropertiesToFetch:

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  • Non-deprecated replacement for NSCalibratedBlackColorSpace?

    - by uliwitness
    I'm implementing my own NSBitmapImageRep (to draw PBM image files). To draw them, I'm using NSDrawBitmap() and passing it the NSCalibratedBlackColorSpace (as the bits are 1 for black, 0 for white). Trouble is, I get the following warning: warning: 'NSCalibratedBlackColorSpace' is deprecated However, I couldn't find a good replacement for it. NSCalibratedWhiteColorSpace gives me an inverted image, and there seems to be no way to get NSDrawBitmap() to use a CGColorSpaceRef or NSColorSpace that I could create as a custom equivalent to NSCalibratedBlackColorSpace. I've found a (hacky) way to shut up the warning (so I can still build warning-free until a replacement becomes available) by just passing @"NSCalibratedBlackColorSpace" instead of the symbolic constant, but I'd rather apply a correct fix. Anybody have an idea?

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  • Controllers in Document-based application

    - by Richard Ibarra
    Hi I've tried to setup a controller for a document in a document based application, and i'm not sure what is the correct for doing that. In MyDocument.xib I have set the File's Owner as MyDocument class and the I connected the outlets and actions to it but it doesn't seem to work Could anybody give me a hand on this? Cheers

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  • iOS Question. Is There a Framework for Build Time Based Apps.

    - by dugla
    I have the need for some time based effects in the iPad app I am building. The UIView class animation capability beginAnimatins/commitAnimations is exactly the sort of thing I am looking for but it is restricted to specific properties of UIView deemed animatable. Ideally, I am looking for a solution that lets me drive an a time-based function that can perhaps send messages to a class of my own choosing at the rate I specify in the animation. Specifically, I have a function - my implementation of the RenderMan function "smoothstep" which is essentially an ease-in ease-out curve common in animation. It takes [0 - 1] as input and outputs [0 - 1] as the curve is evaluated. I want to drive this function for a duration of my own choosing at rate of my own choosing. Thanks in advance. -Doug

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  • Core Data Predicates with Subclassed NSManagedObjects

    - by coneybeare
    I have an AUDIO class. This audio has a SOUND_A subclass and a SOUND_B subclass. This is all done correctly and is working fine. I have another model, lets call it PLAYLIST_JOIN, and this can contain (in the real world) SOUND_A's and SOUND_B's, so we give it a relationship of AUDIO and PLAYLIST. This all works in the app. The problem I am having now is querying the PLAYLIST_JOIN table with an NSPredicate. What I want to do is find an exact PLAYLIST_JOIN item by giving it 2 keys in the predicate sound_a._sound_a_id = %@ && playlist.playlist_id = %@ and sound_b.sound_b_id = %@ && playlist.playlist_id = %@ The main problem is that because the table does not store sound_a and sound_b, but stored audio, I cannot use this syntax. I do not have the option of reorganizing the sound_a and sound_b to use the same _id attribute name, so how do I do this? Can I pass a method to the predicate? something like this: [audio getID] = %@ && playlist_id = %@

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  • NSNull isEqualToString Issue With JSON Response

    - by IconicDigital
    I am getting the following error -[NSNull isEqualToString:]: unrecognized selector sent to instance 0x3c168090 on this line of code cell.offerTitle.text = [voucherData objectForKey:@"offer_title"]; Could someone help me correct the problem please? Thanks Oliver * Update ** NSlog [voucherData objectForKey:@"offer_title"] and I get the following 2012-12-05 16:50:17.512 app.co.uk - Vouchers and Deals[6350:907] <null> 2012-12-05 16:50:17.514 app.co.uk - Vouchers and Deals[6350:907] -[NSNull isEqualToString:]: unrecognized selector sent to instance 0x3c168090 Checked the JSON and there was a null value, I have done the following to check if null but this isn't working if([voucherData objectForKey:@"offer_title"] == NULL){ cell.offerTitle.text = @"INVALID"; }else{ cell.offerTitle.text = [voucherData objectForKey:@"offer_title"]; }

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