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  • What is the performance difference between blocks and callbacks?

    - by Don
    One of the things that block objects, introduced in Snow Leopard, are good for is situations that would previously have been handled with callbacks. The syntax is much cleaner for passing context around. However, I haven't seen any information on the performance implications of using blocks in this manner. What, if any, performance pitfalls should I look out for when using blocks, particularly as a replacement for a C-style callback?

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  • How can I make a UIPickerView like a UIDatePicker?

    - by iamthepiguy
    I have a custom UIViewController subclass which acts as Datasource and Delegate for a UIPickerView which I would like to serve two different purposes, as each are simple enough, and don't really warrant separate files. One operation must be as a custom picker, and this works fine. However, for the other operation, I want it to act just like a UIDatePicker. The problem is, UIDatePicker is a subclass of UIControl, not UIPickerView. Is there any sort of enum value I can set in a method (or other way) that will set the UIPickerView to act as a date picker? Or do I have to make two completely different classes and use them differently (pain in the ass)?

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  • Copying contents from one NSMutableArray to another

    - by Sheehan Alam
    I have two NSMutableArrays: NSMutableArray* currentMessages NSMutableArray* items I am trying to copy the contents of items into currentMessages as such: [self.currentMessages addObjectsFromArray:self.items]; When I am debugging self.items contains 30 objects. After this operation self.currentMessages contains 0 objects. Why is the copy not working?

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  • CoreData and many NSArrayController

    - by unixo
    In my CoreData Application, I've an outline view on left of main window, acting as source list (like iTunes); on the right I display a proper view, based on outline selection. Each view has its components, such as table view, connected to array controller, owned by the specific view. Very often different views display same data, for example, a table view of the same entity. From a performance point of view, is better to have a single array controller per entity and share it between all views or does CoreData cache avoid memory waste?

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  • iPhone, special characters in JSON Response

    - by eddit
    Writing an iphone app, and I'm getting my data from a REST API that returns JSON. My problem is, some of the data has special characters embedded and Im getting errors. Example: MartÌn Petite-RiviËre-Saint-FranÁois Here is my current code: NSString *jsonString = [[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding]; NSMutableArray *tempResults = [[[jsonString JSONValue] objectForKey:@"getRegionResortsLastUpdatedResponse"] objectForKey:@"return"]; Whenever the data has special characters in it "jsonString" return "(null)", otherwise everything works fine. Is this something I can handle on my end, or does the API need to be modified to output the character codes?

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  • Optimize a views drawing code

    - by xon1c
    Hi, in a simple drawing application I have a model which has a NSMutableArray curvedPaths holding all the lines the user has drawn. A line itself is also a NSMutableArray, containing the point objects. As I draw curved NSBezier paths, my point array has the following structure: linePoint, controlPoint, controlPoint, linePoint, controlPoint, controlPoint, etc... I thought having one array holding all the points plus control points would be more efficient than dealing with 2 or 3 different arrays. Obviously my view draws the paths it gets from the model, which leads to the actual question: Is there a way to optimize the following code (inside the view's drawRect method) in terms of speed? int lineCount = [[model curvedPaths] count]; // Go through paths for (int i=0; i < lineCount; i++) { // Get the Color NSColor *theColor = [model getColorOfPath:[[model curvedPaths] objectAtIndex:i]]; // Get the points NSArray *thePoints = [model getPointsOfPath:[[model curvedPaths] objectAtIndex:i]]; // Create a new path for performance reasons NSBezierPath *path = [[NSBezierPath alloc] init]; // Set the color [theColor set]; // Move to first point without drawing [path moveToPoint:[[thePoints objectAtIndex:0] myNSPoint]]; int pointCount = [thePoints count] - 3; // Go through points for (int j=0; j < pointCount; j+=3) { [path curveToPoint:[[thePoints objectAtIndex:j+3] myNSPoint] controlPoint1:[[thePoints objectAtIndex:j+1] myNSPoint] controlPoint2:[[thePoints objectAtIndex:j+2] myNSPoint]]; } // Draw the path [path stroke]; // Bye stuff [path release]; [theColor release]; } Thanks, xonic

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  • Is a tab bar configuration view can be customized ?

    - by Dirty Henry
    I have an application with 8 tabbar items in the tabbar controller. Is there a way I can customize the layout of the "... (more)" view in which you can configure which tab bar items should appear in the main tab bar. It seems to be a table view controller but i'd like to use custom cell views and a background image.

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  • Incompatible Types in Initialization

    - by jack
    I have the following code in a subroutine that produces an incompatible types in initialization error on the varVal library in the subroutine evaluateExpression: NSDictionary *varVal; for (int i=0; i<varCount; i++) { [varVal setObject:[(i+1)*2 stringValue] forKey:[i stringValue]]; } double result =[[self brain] evaluateExpression:[[self brain] expression] usingVariableValues:varVal]; My subroutine declaration in the brain.h file is: +(double)evaluateExpression:(id)anExpression usingVariableValues:(NSDictionary *)variables; I'd appreciate any help.

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  • CGAffineTransformMakeRotation goes the other way after 180 degrees (-3.14)

    - by TheKillerDev
    So, i am trying to do a very simple disc rotation (2d), according to the user touch on it, just like a DJ or something. It is working, but there is a problem, after certain amount of rotation, it starts going backwards, this amount is after 180 degrees or as i saw in while logging the angle, -3.14 (pi). I was wondering, how can i achieve a infinite loop, i mean, the user can keep rotating and rotating to any side, just sliding his finger? Also a second question is, is there any way to speed up the rotation? Here is my code right now: #import <UIKit/UIKit.h> @interface Draggable : UIImageView { CGPoint firstLoc; UILabel * fred; double angle; } @property (assign) CGPoint firstLoc; @property (retain) UILabel * fred; @end @implementation Draggable @synthesize fred, firstLoc; - (id)initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; angle = 0; if (self) { // Initialization code } return self; } -(void)handleObject:(NSSet *)touches withEvent:(UIEvent *)event isLast:(BOOL)lst { UITouch *touch =[[[event allTouches] allObjects] lastObject]; CGPoint curLoc = [touch locationInView:self]; float fromAngle = atan2( firstLoc.y-self.center.y, firstLoc.x-self.center.x ); float toAngle = atan2( curLoc.y-(self.center.y+10), curLoc.x-(self.center.x+10)); float newAngle = angle + (toAngle - fromAngle); NSLog(@"%f",newAngle); CGAffineTransform cgaRotate = CGAffineTransformMakeRotation(newAngle); self.transform = cgaRotate; if (lst) angle = newAngle; } -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch =[[[event allTouches] allObjects] lastObject]; firstLoc = [touch locationInView:self]; }; -(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { [self handleObject:touches withEvent:event isLast:NO]; }; -(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { [self handleObject:touches withEvent:event isLast:YES]; } @end And in the ViewController: UIImage *tmpImage = [UIImage imageNamed:@"theDisc.png"]; CGRect cellRectangle; cellRectangle = CGRectMake(-1,self.view.frame.size.height,tmpImage.size.width ,tmpImage.size.height ); dragger = [[Draggable alloc] initWithFrame:cellRectangle]; [dragger setImage:tmpImage]; [dragger setUserInteractionEnabled:YES]; dragger.layer.anchorPoint = CGPointMake(.5,.5); [self.view addSubview:dragger]; I am open to new/cleaner/more correct ways of doing this too. Thanks in advance.

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  • How to check image during animation

    - by TomTom
    I have set up an animation in the following way (self is an UIImageView, myImages an Array of UIImages): self.animationImages = myImages; self.animationDuration = 50; self.animationRepeatCount = 0; [self startAnimating]; During the animation I'd like to check the current image. I tried it the following way if([self image]==[UIImage imageNamed:@"image1.png"]); but this does not work. Is there a straight forward way for this? Can I keep track of which image is shown during the animation?

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  • Help! Obj-C/Iphone programming: extracting string from html text and reading off line by line

    - by royden
    hihi, I have this html text response from a particular website: <tr><td valign="top"><img src="/icons/image2.gif" alt="[IMG]"></td><td><a href="crsdsdfs2221.jpg">crash-2221.jpg</a></td><td align="right">14-Jun-2010 14:29 Notice for every line, there is this href=".__", which is an image file with random name and random format. I would like to extract that string within the inverted commas out so that i can append it into a URL path and download the image. I've been looking through this documentation from apple: http://developer.apple.com/mac/library/documentation/cocoa/conceptual/strings/Articles/SearchingStrings.html#//apple_ref/doc/uid/20000149-CJBBGBAI on String programming but couldn't find one that fits my bill. Also after reading it, what code can I use to ensure that I will be reading the next line the next time my function is called( because I want to download the next picture). Hope some kind soul can help me out, thanks!

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  • how to reloadData in tableView when tableview access data from database.

    - by Ajeet Kumar Yadav
    I am new in iphone i am developing a application that take value from data base and display data in tableview. in this application we save data from one data table to other data table this is when add first time work and when we do second time application is crash. how to solve this problem i am not understand code is given bellow my appdelegate code for insert value from one table to other is given bellow -(void)sopinglist { //////databaseName= @"SanjeevKapoor.sqlite"; databaseName =@"AjeetTest.sqlite"; NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDir = [documentPaths objectAtIndex:0]; databasePath =[documentsDir stringByAppendingPathComponent:databaseName]; [self checkAndCreateDatabase]; list1 = [[NSMutableArray alloc] init]; sqlite3 *database; if (sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { if(addStmt == nil) { ///////////const char *sql = "insert into Dataa(item) Values(?)"; const char *sql = " insert into Slist select * from alootikki"; ///////////// const char *sql =" Update Slist ( Incredients, Recipename,foodtype) Values(?,?,?)"; if(sqlite3_prepare_v2(database, sql, -1, &addStmt, NULL) != SQLITE_OK) NSAssert1(0, @"Error while creating add statement. '%s'", sqlite3_errmsg(database)); } /////for( NSString * j in k) sqlite3_bind_text(addStmt, 1, [k UTF8String], -1, SQLITE_TRANSIENT); //sqlite3_bind_int(addStmt,1,i); // sqlite3_bind_text(addStmt, 1, [coffeeName UTF8String], -1, SQLITE_TRANSIENT); // sqlite3_bind_double(addStmt, 2, [price doubleValue]); if(SQLITE_DONE != sqlite3_step(addStmt)) NSAssert1(0, @"Error while inserting data. '%s'", sqlite3_errmsg(database)); else //SQLite provides a method to get the last primary key inserted by using sqlite3_last_insert_rowid coffeeID = sqlite3_last_insert_rowid(database); //Reset the add statement. sqlite3_reset(addStmt); // sqlite3_clear_bindings(detailStmt); //} } sqlite3_finalize(addStmt); addStmt = nil; sqlite3_close(database); } And the table View code for access data from database is given bellow SanjeevKapoorAppDelegate *appDelegate =(SanjeevKapoorAppDelegate *)[[UIApplication sharedApplication] delegate]; [appDelegate sopinglist]; ////[appDelegate recpies]; /// NSArray *a =[[appDelegate list1] componentsJoinedByString:@","]; k= [[appDelegate list1] componentsJoinedByString:@","];

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  • Why am I getting a EXC_BAD_ACCESS in a NSTimer selector?

    - by AngeDeLaMort
    I've got quite a weird problem. To make it short, i'll write some pseudo-code: init: create a dictionary and insert n elements. create a "repeat timer" and add it to the currentRunLoop using the timerRefresh selector. timerRefresh: using a list of keys, find the items in the dictionary if the item exists -> call a function So, for an unknown reason, I get an EXC_BAD_ACCESS when I do: [item function]; But I traced the address I got from the dictionary items and it's ok. The ref count of the items in the dictionary is still 1. The {release, dealloc} of the items in the dictionary aren't called. Everything seems fine. Also, to make it worst, it works for some items. So, I'm wondering if there is a threading problem? or something else obscure? The callstack is quite simple: #0 0x93e0604b in objc_msgSend_fpret #1 0x00f3e6b0 in ?? #2 0x0001cfca in -[myObject functionm:] at myObject.m:000 #3 0x305355cd in __NSFireTimer #4 0x302454a0 in CFRunLoopRunSpecific #5 0x30244628 in CFRunLoopRunInMode #6 0x32044c31 in GSEventRunModal #7 0x32044cf6 in GSEventRun #8 0x309021ee in UIApplicationMain #9 0x000027e0 in main at main.m:14 So, any suggestion where to look would be appreciated.

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  • How to backup data stored with Core Data - iPhone app?

    - by Alex
    I'm using sqlite for the persistent store, so could I just upload the .sqlite file to, for example, Amazon S3 as a way of providing users with the ability to backup their app data? Then for restoring just download it back and replace the existing .sqlite file in the app's folder. Does anybody see any issues with that? Has anyone done it? Any other suggestions on how to implement data backup feature?

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  • Best practices and Design Patterns for iPhone forms?

    - by cannyboy
    Part of the app I'm making requires the user to fill in a multi-page form, the contents of which will be saved locally (perhaps using Core Data). Are there any best practices for this? This form just includes text fields. I guess the options are UITextFields, or perhaps a UIWebView, with the fields as part of an html form? Are there are any best practices, or design patterns, which are good for this kind of thing?

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  • How do I create an NSArray with string literals?

    - by Kyle
    I'm attempting to create an NSArray with a grouping of string literals, however I get the compile error "Initializer element is not constant". NSArray *currencies = [NSArray arrayWithObjects:@"Dollar", @"Euro", @"Pound", nil]; Could someone point out what I'm doing wrong, and possibly explain the error message?

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  • How to make AVAudioPlayer play once it is stopped?

    - by Viral
    hi friends, I am using AVAudioplayer to play some sound. But once I make it stop using [player stop](where player is the object of AVAudioplayer] It is not starting again to play after some time when I call method [player play], So can any one tell me how to do the same in my application?? The play will again call using NSTimer method, after some delay of time. Thanks in advance...

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  • Unexpected key-value behavior in a Core Data Context

    - by ????
    If I create an array of strings (via key-value coding) containing the names of a Managed Object entity's attributes which are stored in the App Delegate the first time, I get an array of NSStrings without any problems. If I subsequently make the same call later from the same entry point in code, that same collection becomes an array of NULL objects- even though nothing in the Core Data Context has changed. One unappealing work-around involves re-creating the string array every time, but I'm wondering if anyone has a guess as to what's happening behind the scenes. // Return an array of strings with the names of attributes the Activity entity - (NSArray *)activityAttributeNames { #pragma mark ALWAYS REFRESH THE ENTITY NAMES? //if (activityAttributeNames == nil) { // Create an entity pointer for Activity NSEntityDescription *entity = [NSEntityDescription entityForName:@"Activity" inManagedObjectContext:managedObjectContext]; NSArray *entityAttributeArray = [[NSArray alloc] initWithArray:[[entity attributesByName] allValues]]; // Extract the names of the attributes with Key-Value Coding activityAttributeNames = [entityAttributeArray valueForKeyPath:@"name"]; [entityAttributeArray release]; //} return activityAttributeNames; }

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  • Faking a UITableView selection

    - by John Smith
    I have a UITableView where a selection displays some cool stuff in another part of the display. I tried to fake a keypress by writing: NSIndexPath *ip = [NSIndexPath indexPathForRow: 1 inSection:0]; [tableView selectRowAtIndexPath:ip animated:NO scrollPosition:UITableViewScrollPositionTop ]; [self tableView:tableView didSelectRowAtIndexPath:ip]; However it seems the last line is not being run. How can I make it run?

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