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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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  • iPhone: How do I override the back button in a Navigation Controller?

    - by Angelo Stracquatanio
    Hello, In my app I have a basic Navigation Controller. For all of my views, except one, the controller works as it should. However, for one view in particular, I would like the 'back' button to not go back to the previous view, but to go to one I set. In particular it is going to go back 2 views and skip over one. After doing some research I found that I can intercept the view when it disappears, so I tried to put in code to have it navigate to the page I would like: - (void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; //i set a flag to know that the back button was pressed if (viewPushed) { viewPushed = NO; } else { // Here, you know that back button was pressed mainMenu *mainViewController = [[mainMenu alloc] initWithNibName:@"mainMenu" bundle:nil]; [self.navigationController pushViewController:mainViewController animated:YES]; [mainViewController release]; } } That didn't work, so does anyone have any ideas? Thanks!!

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  • UIButton not being clicked in iPhone programming.

    - by suse
    Hello, I've created a UIButton on a view and on action of the UIButton[UIButton* button1_obj] one more button[UIButton* button2_obj] is created on same view. i'm facing these 2 issues...please guide me how to proceed. button1_obj is appearing when i run my project, but its not being clicked or highlighted, nor any exception is thrown. On action of button1_obj , button2-obj has to appear on the same view, how to clear the view before placing button2_obj on it.

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  • iphone In app purchase

    - by edie
    Hi... I'm adding in-app purchase on my application. I have a view that displays information about the product and one button for purchasing the product. My question was how can I stop the user to tap again the buy button so that the StoreManager will only call my Buy method once? Because sometimes I had tapped it twice that's why two alertView shows up asking about the purchase. Should I set the button "enabled property" to no after I tap. Any suggestions that would be good about this... thanks in advance.

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  • How do I change the UIView programmatically?

    - by user317834
    I have created View A and View B. My window has View A displayed on the screen. I also have a UIButton on View A. I want to switch from View A to View B when I click on the Button. I am not using any UIViewController. Is it possible to switch the views without using controller? I am calling buttonAction method on TOUCHUPINSIDE The problem is that it doesn't do anything when I say [ViewA removeFromSuperView]; What should I do now?

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  • iPhone --- 3DES Encryption returns "wrong" results?

    - by Jan Gressmann
    Hello fellow developers, I have some serious trouble with a CommonCrypto function. There are two existing applications for BlackBerry and Windows Mobile, both use Triple-DES encryption with ECB mode for data exchange. On either the encrypted results are the same. Now I want to implent the 3DES encryption into our iPhone application, so I went straight for CommonCrypto: http://www.opensource.apple.com/source/CommonCrypto/CommonCrypto-32207/CommonCrypto/CommonCryptor.h I get some results if I use CBC mode, but they do not correspond with the results of Java or C#. Anyway, I want to use ECB mode, but I don't get this working at all - there is a parameter error showing up... This is my call for the ECB mode... I stripped it a little bit: const void *vplainText; plainTextBufferSize = [@"Hello World!" length]; bufferPtrSize = (plainTextBufferSize + kCCBlockSize3DES) & ~(kCCBlockSize3DES - 1); plainText = (const void *) [@"Hello World!" UTF8String]; NSString *key = @"abcdeabcdeabcdeabcdeabcd"; ccStatus = CCCrypt(kCCEncrypt, kCCAlgorithm3DES, kCCOptionECBMode, key, kCCKeySize3DES, nil, // iv, not used with ECB plainText, plainTextBufferSize, (void *)bufferPtr, // output bufferPtrSize, &movedBytes); t is more or less the code from here: http://discussions.apple.com/thread.jspa?messageID=9017515 But as already mentioned, I get a parameter error each time... When I use kCCOptionPKCS7Padding instead of kCCOptionECBMode and set the same initialization vector in C# and my iPhone code, the iPhone gives me different results. Is there a mistake by getting my output from the bufferPtr? Currently I get the encrypted stuff this way: NSData *myData = [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)movedBytes]; result = [[NSString alloc] initWithData:myData encoding:NSISOLatin1StringEncoding]; It seems I almost tried every setting twice, different encodings and so on... where is my error?

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  • How to search on a array and display the items on tableview using a searchbar?

    - by skiria
    Hi, I would like to search on a arrays hierachy and display the results on a tableview. The tableview is empty when we run the app and the, when we search it, the data is written. What's the best way to do this? I read tutorials wich explains how it search on a tableview, but i want to search in all of arrays hierachy. I have 3 classes class video //iVars to allocate the video metadata NSInteger videoID; NSString *nameVideo; NSString *nameCategory; NSString *nameTopic; NSString *user; NSString *date; NSString *description; NSString *urlThumbnail; NSString *urlVideo; class Topic NSInteger TopicId; NSString nameTopic; NSMutableArray videos; class Category NSInteger CategoryId; NSString nameCategory NSMutableArray topics AppDelegate NSMutableArray categories

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  • Implementing Tagging using Core Data on the iPhone

    - by Jonathan Penn
    I have an application that uses CoreData and I'm trying to figure out the best way to implement tagging and filtering by tag. For my purposes, if I was doing this in raw SQLite I would only need three tables, tags, item_tags and of course my items table. Then filtering would be as simple as joining between the three tables where only items are related to the given tags. Quite straightforward. But, is there a way to do this in CoreData and utilizing NSFetchedResultsController? It doesn't seem that NSPredicate give you the ability to filter through joins. NSPredicate's aren't full SQL anyway so I'm probably barking up the wrong tree there. I'm trying to avoid reimplementing my app using SQLite without CoreData since I'm enjoying the performance CoreData gives me in other areas. Yes, I did consider (and built a test implementation) diving into the raw SQLite that CoreData generates, but that's not future proof and I want to avoid that, too. Has anyone else tried to tackle tagging/filtering with CoreData in a UITableView with NSFetchedResultsController

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  • NSManagedObjectContext returns YES for hasChanges when there are none

    - by JK
    I created a separate NSManagedObjectContext on a separate thread to perform some store maintenance. However, I have noticed that the context returns YES for hasChanges as soon as a managed object in it is even referenced e.g. NSString *name = managedObject.name; This context is created and used exclusively in 1 method. Why is it returning has changes, when there there are none?

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  • Is there a way to set an int to 001

    - by H.aLFaRSi
    i need to set an integer to start from 001 instead of only 1 int iNumber = 001; NSLog(@"%d",iNumber); // this is logging 1 instead of 001 is there a possible way to make it 001 ? [UPDATED] i need this because i`m creating an NSMutableArray from NSUserDefaults, after that I'm sorting the array using NSSortDescriptor. the problem is because i can't set the int to start from 001 the array i sorted like this 0, 10, 11, 12, 1, 2, 3, 4, 5, 6, 7, 8, 9. More Code explained NSString *name = @"Name"; NSUserDefaults *MainArray = [NSUserDefaults standardUserDefaults]; NSString *Temp = [NSString stringWithFormat:@"%@%d", name,MainNumber]; [MainArray setObject:@"test" forKey:Temp]; [MainArray synchronize]; NSLog(@"%@",Temp); MainNumber++; the above code will save it like this : Name1,Name2,Name3.... i need it to be Name001, Name002, Name003 ....... thank you in advance :)

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  • How to make a macro which gives back a string into the source code?

    - by mystify
    Example: I want to do this: METHODNAME(5) { // do something } which results in: - (void)animationStep5 { // do something } Is there any way to do this? Basically, what I need is a way to generate a real source code string before the program is compiled, so the compiler does see - (void)animationStep5... Or maybe there's something different than a macro, which can help here to auto-generate method names (not at run-time)?

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  • FBConnect Demo Application

    - by gmcalab
    I am running the demo application that is supplied with the facebook-ios-sdk. The application starts in the emulator, with a LogIn button. I click the button which then launches safari to grant access to the application. I log in with my fb creds and allow the application. I am the administrator for the application and I have verified I put in the right app key. After I allow access, it says "Safari cannot open the page because the address in invalid"...this is the url it's trying to go to: http://www.facebook.com/connect/uiserver.php... So am I missing something because the breakpoint for (void)fbDidLogin never gets hit...

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  • how do I set a delegate in a view that is not my main view

    - by orangecl4now
    I have a xib. the xib has a button that swaps another xib. the second xib has a uitextfield and a uilabel. how do I make the keyboard go away when I'm done typing? what do I need to wire or code? the second xib has it's own class (called CustomSign.m) Inside CustomSign.m, I've implemented the following method -(void)textFieldDidEndEditing:(UITextField *)textField { [customText resignFirstResponder]; signedLabel.text = customText.text; } - (void)awakeFromNib { //assume textField is an ivar that is connected to the textfield in IB [customText setDelegate:self]; } I get the following warning Class "CustomSign" does not implement the UITextFieldDelegate protocol

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  • iPhone toolbar shared by multiple views

    - by codemonkey
    Another iPhone noob question. The app I'm building needs to show a shared custom UIToolbar for multiple views (and their subviews) within a UITabBarController framework. The contents of the custom toolbar are the same across all the views. I'd like to be able to design the custom toolbar as a xib and handle UI events from its own controller class (I'm assuming I can subclass UIToolbar to do so?). That way I could define IBOutlet & IBAction items, etc. Then I could associate this custom toolbar with eachs of the UITabBarController views (and their subviews). But I'm having trouble finding out whether that's possible - and if so, how to do it. In particular, I want to be able to push new views onto UINavigationControllers that are each associated with parent UITabBarController tabs. So, to summarize, I want a: custom toolbar shared by multiple views which are managed by multiple navigation controllers and the navigation controllers are associated with different tabs of a parent tab bar controller The tab bar controller itself is launched modally, though I don't believe that's relevant. Anyway, the tab bar controller is working, as are its child navigation controllers. I'm just having a little trouble figuring out how to persist the shared toolbar to the various subviews. I'd settle for a good clean way of implementing programmatically... though I'd prefer the flexibility of keeping the toolbar's visual design in a xib. Anyone have any suggestions?

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  • Comparing floats in their bit representations

    - by sczizzo
    Say I want a function that takes two floats (x and y), and I want to compare them using not their float representation but rather their bitwise representation as a 32-bit unsigned int. That is, a number like -495.5 has bit representation 0b11000011111001011100000000000000 or 0xC3E5C000 as a float, and I have an unsigned int with the same bit representation (corresponding to a decimal value 3286614016, which I don't care about). Is there any easy way for me to perform an operation like <= on these floats using only the information contained in their respective unsigned int counterparts?

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  • pointer being freed was not allocated

    - by kudorgyozo
    Hello i have the following error: malloc: * error for object 0x2087000: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug I have no idea what object that is. I don't know how to find it. Can anybody explain to me how (and where) to use malloc_history. I have set a breakpoint in malloc_error_break but i couldn't find out what object is at that address. I receive this after removing an object from an nsmutablearray and popping a view controller manually. If I comment out the line [reviewUpload.images removeObject: self.reviewUploadImg] it doesn't give me the error but of course it's not useful for me like that. - (void) removeImage { debugLog(@"reviewUploadImg %@", self.reviewUploadImg); debugLog(@"reviewUpload %@", self.reviewUpload); debugLog(@"reviewUploadImg thumb %@", self.reviewUploadImg.thumb); [reviewUpload.images removeObject: self.reviewUploadImg]; [self.navigationController popViewControllerAnimated:TRUE]; }

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  • Why does this TableView code work?

    - by nevan
    I made a typo when creating a UITableViewCell with this code: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"CellIdentifier"; UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { NSLog(@"Creating cell"); cell = [[[UITableViewCell alloc] initWithStyle:UITableViewStylePlain reuseIdentifier:CellIdentifier] autorelease]; } cell.textLabel.text = @"Hello"; return cell; } The typo is in using UITableViewStylePlain instead of UITableViewCellStyleDefault. The code worked fine, creating new cells. Why?

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  • Cocoa Bindings in the face of a million of items in an NSArray

    - by François Beausoleil
    I'm writing a GUI for MongoDB using Cocoa. It's going well, but I don't know how to make KVO properties that would be lazily loaded. How does one handle that? For instance, viewing the documents in a Mongo collection. The collection might have a million items in it. I suspect I shouldn't be downloading the full 2-5 GiB of data to my Cocoa app, then format and display 20 rows. How does one implement that? I called my project Mongo Explorer, available on GitHub. Specifically, how would I code MECollection#reload to be lazy? Do I need to implement a data source delegate for my NSTableView?

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  • NSOperationqueue i want to block main thread

    - by alexeyndru
    i want to block the main thread until something else is done in the background. i used: result=[self performSelectorInBackground:@selector(calculate:) withObject:expression]; just bellow this line I am using result: [self use:result]; i dont want to use result until it is available. to achieve this I implemented calculate: { [[(AppDelegate *)[[UIApplication sharedApplication] delegate] queue] waitUntilAllOperationsAreFinished]; calculating result... } and still, the result is used before it is calculated. so, i didnt block the main thread. pls help me do that. thanks

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  • How do I change the color of a Cocos2d MenuItem?

    - by Rob Sawyer
    [MenuItemFont setFontSize:20]; [MenuItemFont setFontName:@"Helvetica"]; //I'm trying to change the color of start (below item) MenuItem *start = [MenuItemFont itemFromString:@"Start Game" target:self selector:@selector(startGame:)]; MenuItem *help = [MenuItemFont itemFromString:@"Help" target:self selector:@selector(help:)]; Menu *startMenu = [Menu menuWithItems:start, help, nil]; [startMenu alignItemsVertically]; [self add:startMenu];

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