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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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• Trouble in type casting or any ideas ???

  - by ahmet732

  I write code below but it gives warning.. I identified dbdesc as a NSString but nothing changes.. How will I handle with this type of warnings? **[self.searchDetailViewController setText:appDelegate.dbdesc];** warning:'searchDetailViewController' may not respond to 'setText:' (Messages without a message method signatures will be assumed to return (id) and accept '...'as arguments )

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• NSNotifications vs delegate for multiple instances of same protocol

  - by Brent Traut

  I could use some architectural advice. I've run into the following problem a few times now and I've never found a truly elegant way to solve it. The issue, described at the highest level possible:I have a parent class that would like to act as the delegate for multiple children (all using the same protocol), but when the children call methods on the parent, the parent no longer knows which child is making the call. I would like to use loose coupling (delegates/protocols or notifications) rather than direct calls. I don't need multiple handlers, so notifications seem like they might be overkill. To illustrate the problem, let me try a super-simplified example: I start with a parent view controller (and corresponding view). I create three child views and insert each of them into the parent view. I would like the parent view controller to be notified whenever the user touches one of the children. There are a few options to notify the parent: Define a protocol. The parent implements the protocol and sets itself as the delegate to each of the children. When the user touches a child view, its view controller calls its delegate (the parent). In this case, the parent is notified that a view is touched, but it doesn't know which one. Not good enough. Same as #1, but define the methods in the protocol to also pass some sort of identifier. When the child tells its delegate that it was touched, it also passes a pointer to itself. This way, the parent know exactly which view was touched. It just seems really strange for an object to pass a reference to itself. Use NSNotifications. The parent defines a separate method for each of the three children and then subscribes to the "viewWasTouched" notification for each of the three children as the notification sender. The children don't need to attach themselves to the user dictionary, but they do need to send the notification with a pointer to themselves as the scope. Same as #4, but rather than using separate methods, the parent could just use one with a switch case or other branching along with the notification's sender to determine which path to take. Create multiple man-in-the-middle classes that act as the delegates to the child views and then call methods on the parent either with a pointer to the child or with some other differentiating factor. This approach doesn't seem scalable. Are any of these approaches considered best practice? I can't say for sure, but it feels like I'm missing something more obvious/elegant.

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• How to call a method from another class that's been instantiated within the current class

  - by Pavan

  my screen has a few views like such __________________ | _____ | | | | | //viewX is a video screen | | | | | viewX | vY | | //viewY is a custom uiview i created. | |____| | //it contains a method which i would like to call that toggles |_________________| //the hidden property of this view. and when it hides, a little | | //button is replaced no the top right corner on top of viewX | viewZ | //the video layer | | |_________________| //viewZ is a view containing many square views - thumbnails. my question is, i dont know how to register for touch events so that it recognises any touch event on no matter which view the user touches the screen.. atm im handling the touch events for each view inside it. so all works well... however what im trying to do is that when the user taps anywhere else on the screen but on viewY, viewY should dissapear by calling that method in the viewY class. this viewY class is instantiated and has no xib file attached to it. the uiview is created progammatically in the viewY class. this whole class for viewY behviour is instantiated in viewX - the video view. my boss says add delegates.. although i have now clue how to do that... any help? is there anyway i can just make it really simple and be able to say REMOVE VIEW no matter which class im calling from? Also ive seen other people achieve this by using these funky arrows - ... <- etc.. although im not sure if thats what i need or how to implement such a thing. ah i think ive made my question quite complicated but i really mean it to be a simple one, and know it can be done in an easy way!

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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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• How is an AppDelegate instanciated?

  - by pwny

  I have an iOS application for which I want to create a ViewController programmatically. I started an empty XCode project and modified the main method so it looks like this int main(int argc, char *argv[]) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, @"MyAppDelegate_iPad"); [pool release]; return retVal; } The app is a Universal Application, MyAppDelegate_iPad is a subclass of MyAppDelegate, which is a subclass of NSObject <UIApplicationDelegate>. My problem is that the applicationDidFinishLoading method I've overridden in MyAppDelegate_iPad is never called (break point on the first line never hits). The method looks like this -(void) applicationDidFinishLaunching:(UIApplication *)application { window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; if(!window) { [self release]; return; } window.backgroundColor = [UIColor whiteColor]; rootController = [[MyViewController alloc] init]; [window addSubview:rootController.view]; [window makeKeyAndVisible]; [window layoutSubviews]; } I removed the line to link to a nib file from my plist file (I used to get the default "My Universal app on iPad" white screen) and now all that is displayed is a black screen. applicationDidFinishLoading is still not being called. Am I doing something wrong? How should I properly create my AppDelegate instance?

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• iPhone app not running on iPhone

  - by Jon

  I have my iPhone setup on my computer at home, with my developer account and provisioning profile. I'm trying to get it setup on my work computer so I can run work apps on it as well. My work has their own dev account. I created an app ID and privisioning profile on my personal account and downloaded it on my work computer but its not letting me compile and run on my iPhone. It says valid provisiong profile not found on executable.

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• save the song in iphone through application

  - by riteshkumar1905

  I have completed the code to play song using url connection.. now how can i save it in iphone. thnx

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• drawRect gets called on UIView subclass but not on UIViewController

  - by HotFudgeSunday

  My code is working so far but I had to create a Class for the UIView. This is a bit inconvenient because I need to interact with the ViewController too. BTW, I did try [self setNeedsDisplay] on the ViewDidLoad of the UIViewController subclass file but it didn't work. Here's the code, which works on UIView Subclass but doesn't get called on a UIViewController one: - (void)drawRect:(CGRect)rect { UIColor *currentColor = [UIColor redColor]; CGContextRef context = UIGraphicsGetCurrentContext(); someNum = 1; CGContextBeginPath(context); CGContextMoveToPoint(context, 30, 40); [self addDotImageX:30 andY:40]; CGContextSetLineWidth(context, 2); CGContextSetStrokeColorWithColor(context, currentColor.CGColor); CGContextStrokePath(context); } Any ideas on what to try? BTW, this is a TabBar App. I know those can somehow block the calls to drawRect. The Tabs where created programatically, not through a Nib. Eg: NSMutableArray *listOfViewControllers = [[NSMutableArray alloc] init]; UIViewController *vc; vc = [[Education alloc] init]; vc.title = @"Education"; [listOfViewControllers addObject:vc]; vc.tabBarItem.image = [UIImage imageNamed:@"info.png"]; [vc release]; I would appreciate any ideas. I've been through the answers on this site related to setNeedsDisplay not calling drawRect and haven't found an answer for my particular case. Thanks.

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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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• Mail Composer Address Problem

  - by Arun Sharma

  I found email composer sample code from iphone OS Ref Library. Here is a code- Code: NSArray *toRecipients = [NSArray arrayWithObject:@"[email protected]"]; NSArray *ccRecipients = [NSArray arrayWithObjects:@"[email protected]", @"[email protected]", nil]; NSArray *bccRecipients = [NSArray arrayWithObject:@"[email protected]"]; My question is how to take user's input? Here all email address are predefined in code. so what are the IDs of to, CC, Bcc, subject and body fields?

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• how can i get an offline version of the iphone development handbook?

  - by sarmenhba

  how can i get an offline version of the iphone development handbook?

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• UIView as dictionary key?

  - by subw

  I want to have a NSDictionary that maps from UIViews to something else. However, since UIViews do not implement the NSCopying protocol, I can't use them directly as dictionary keys.

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• How to Call JAX-WS Web Service in Iphone

  - by user128647

  Hello, How to use JAX-WS Web service in Iphone Sdk, anyone has idea then please let me know. Thank You.

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• Can I refer to NSDictionary items numerically?

  - by cannyboy

  I'm trying to set up a UITableView which acts as a form. Each cell has within it a UILabel and a UITextField, so one cell is: Name <enter name> ^ ^ UILabel UITextField Now, I'm trying to populate the UILabel and the UITextField from a NSDictionary (from a plist), where it's organized like so: Root Type Value Name String Address String City String etc But in order to get the right labels and textfields in the cellForRowAtIndexPath method, I would have to refer to the Dictionary numerically. Is there any way to do that?

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• How to make a private property?

  - by mystify

  I tried to make a private property in my *.m file: @interface MyClass (Private) @property (nonatomic, retain) NSMutableArray *stuff; @end @implementation MyClass @synthesize stuff; // not ok Compiler claims that there's no stuff property declared. But there's a stuff. Just in an anonymous category. Let me guess: Impossible. Other solutions?

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• Iphone sdk - How to setup a 'template'

  - by Dave

  I've been working on a Cook Book App and I've been making each page individually which takes a really long time to do, I asked a question similar to this and it was brought to my attention that you can setup a way to automate the design process so all you need to do is input your data. Can someone please explain in as much detail as possible how you setup your xcode files/code to automate this process Thanks

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• How to have Xcode find the newest version of a file

  - by Arian

  Currently I have a SQLite database, that is set statically to use database01.sqlite... but what I need is a way to have the file path find the newest version of the database file that exists. For example: If a database file of database04.sqlite is available, it should use that one instead. Below is my current code: NSString *databaseDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; NSString *filePath = [databaseDirectory stringByAppendingPathComponent:@"database01.sqlite"];

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• Why does Custom UITableViewCell *sometimes* cause an NSInvalidArgumentException?

  - by Wayne Hartman

  I have created a custom UITableViewCell, but when I dequeue the cell, sometimes it throws an NSInvalidArgumentException: [UITableViewCell nameLabel]: unrecognized selector sent to instance 0x3b4e7f0 Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[UITableViewCell nameLabel]: unrecognized selector sent to instance 0x3b4e7f0' Now, my custom UITableViewCell does have an attribute nameLabel, so I am confused why it is throwing this error. Below is the code I use to dequeue the cell: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { NSUInteger row = [indexPath row]; CTMenuItemVO* key = [[[self retrieveCartItems] allKeys] objectAtIndex:row]; NSNumber* quantity = [[self retrieveCartItems] objectForKey:key]; static NSString* SectionsTableIdentifier = @"SectionsTableIdentifier2"; OrderItemCell* cell = (OrderItemCell*)[tableView dequeueReusableCellWithIdentifier: SectionsTableIdentifier]; if (cell == nil) { NSArray* topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"OrderItemCell" owner:nil options:nil]; for(id currentObject in topLevelObjects) { if ([currentObject isKindOfClass:[UITableViewCell class]]) { cell = (OrderItemCell*) currentObject; break; } } } cell.nameLabel.text = key.Name; cell.qtyLabel.text = [quantity stringValue]; return cell; }

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• EXC_MEMORY_ACCESS when trying to delete from Core Data ($cash solution)

  - by llloydxmas

  I have an application that downloads an xml file, parses the file, and creates core data objects while doing so. In the parse code I have a function called 'emptydatacontext' that removes all items from Core Data before creating replacements items from the xml data. This method looks like this: -(void) emptyDataContext { NSFetchRequest * allCon = [[NSFetchRequest alloc] init]; [allCon setEntity:[NSEntityDescription entityForName:@"Condition" inManagedObjectContext:managedObjectContext]]; NSError * error = nil; NSArray * conditions = [managedObjectContext executeFetchRequest:allCon error:&error]; DebugLog(@"ERROR: %@",error); DebugLog(@"RETRIEVED: %@", conditions); [allCon release]; for (NSManagedObject * condition in conditions) { [managedObjectContext deleteObject:condition]; } // Update the data model effectivly removing the objects we removed above. //NSError *error; if (![managedObjectContext save:&error]) { DebugLog(@"%@", [error domain]); } } The first time this runs it deletes all objects and functions as it should - creating new objects from the xml file. I created a 'update' button that starts the exact same process of retrieving the file the proceeding with the parse & build. All is well until its time to delete the core data objects. This 'deleteObject' call creates a "EXC_BAD_ACCESS" error each time. This only happens on the second time through. Captured errors return null. If I log the 'conditions' array I get a list of NSManagedObjects on the first run. On the second this log request causes a crash exactly as the deleteObject call does. I have a feeling it is something very simple I'm missing or not doing correctly to cause this behavior. The data works great on my tableviews - its only when trying to update I get the crashes. I have spent days & days on this trying numerous alternative methods. Whats left of my hair is falling out. I'd be willing to ante up some cash for anyone willing to look at my code and see what I'm doing wrong. Just need to get past this hurdle. Thanks in advance for the help!

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• Class-Dump Installation

  - by sj-dev

  So this may sound like a really stupid question and I HAVE looked at the how-to from the parent website, but no matter what I do, I cannot get this program to even start to install... I tried entering: cd /opt/local/bin/portslocation/dports/class-dump which returned a "this file/director doesnt exist" error, so i tried to get to it folder by folder. when i got all the way to: cd /opt/local/bin/ i cannot go any further. when i check the contents of the bin directory, the only files i can find are (and i cannot access these apparently either): "daemondo port portf portindex portmirror" i have tried doing this on 2 computers so far to no avail, macports is installed on both like the website said and i am having trouble finding any support for it. please and thank you!!

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• CoreData: migration from 2 models

  - by Yola

  I have general app model, after was released any body can do plug-in for it, this plug-in can determine new db parts which merged with my general db. After some time i 'll release new db version^ and plug-in writers may release new version of their dbs. So i need map old version of merged db into new version. How i can do this?

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• Missing HID_Utilities.h on Mac OS X

  - by Jonas Byström

  I'm trying to build with IO for Mac, but I don't seem to have the file with friends installed. When I googled for it, it seemed to me like it was part of, or related to, glut implementation on Mac? Glut is installed. What do I need to do?

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• Iphone SDK - tap to undo a zoom inside of a scroll view

  - by Dave

  Hi, I was just wondering how I can get a single tap to undo the zoom inside of a scroll view? I cant seem to figure it out. I was also wondering how do you know what size to set your scroll view contentSize, as I find this issue a little confusing at the moment I have it set at 460x320. Thanks

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• Are @property's necessary for Interface Builder?

  - by Rits

  In my UIViewController subclass, I have 3 UIView's with each a @property as an IBOutlet. I do not use these properties at all in my code. The views get instantiated as soon as the view controller is created and they are deallocated when the view controller is deallocated. I was thinking; can't I just remove the @property's? I did, and I could still connect my instance variables (with IBOutlet) in Interface Builder. So my question now is; is there any use for properties in combination with Interface Builder, or is it OK to leave them out? Is it required for some memory management or something? Or are they really just for use in your own code? And if I do leave them out, do I still need to release them in dealloc?

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