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  • The right approach to loading dynamic content into a UITableView in iOS

    - by OS.
    ok, I've read tons of bits and pieces on the subject of loading dynamic content (from the web) into a UITableView and the problem with calculating cell height upfront. I've tried different simple implementations but the problem persists... Assuming I need to read a JSON file from the web, parse it into 'item' objects, each with variable size image and various text labels, here is what I believe would be the right approach to avoid long hang time of the app while everything is loading: on app load read JSON file and parse into items array provide only small part of the items array to the tableview (about 10 items) - since I need to load the images associated with each item to calculate cell height - I don't want the view to go through the whole items list and load all images - this hangs the app until every image is loaded display the tableview with the available cells (assuming I load a few 'spare' ones, user can even scroll to more items) in the background using Grand Central Dispatch download images for all/some of the remaining items and then reload the tableview with the new data (repeat step 4 if item list is very long) Step 2 above is necessary since I have no way to calculate the cell height without loading the images first, and since tableview first calculates height of all cells it may take a very long time to download all images for all items. Would you say this is the right approach? am I missing something?

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  • Develop an iPhone / iPad Reader app from scratch

    - by Comma
    I'm developing a reader app for viewing and highlighting proprietary format documents. The documents are 2D. (Might add some cool page flip effects) The interface is similar to that of mobile safari. I have no prior experience with iOS development. Could you guys point me to the right direction? (Things I need to consider, tutorials, sample projects...) THX

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  • iPhone: Get value in multi-dimentional array

    - by Nic Hubbard
    I have an array that is many levels deep and I am wondering what is the best way to get one of the child element values that is deep in my array. I assume I need to use a recursive method, but what is the best way to do this? Or is there a faster way to do this? The array comes from an XML Parser that I am using which builds everything into an array like this (using NSLog to show the structure): { children = ( { children = ( { children = ( { children = ( ); data = 12; element = AssetID; } ); data = ""; element = "ns1:GetUserIdByUsernameResponse"; } ); data = ""; element = "SOAP-ENV:Body"; } ); data = ""; element = "SOAP-ENV:Envelope"; } What I would like to get at is the AssetID data, which in this case is 12.

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  • how to create an object using self?

    - by Nick
    I thought I understood the use of self while referring to anything in the current class. After encountering this warning and subsequent run failure, I have googled many variants of "define self" or "usage of self" and gotten nowhere. This problem is how to create an object without the warning, and understand why. #import <Cocoa/Cocoa.h> @interface Foo : NSObject { Foo *obj; } -(void)beta; @end #import "Foo.h" @implementation Foo -(void)beta{ obj = [self new]; // 'Foo' may not respond to '-new' } @end Note, if I substitute Foo for self, there's no problem. I thought the class name and self were equivalent, but obviously the compiler doesn't think so. Perhaps an explanation of what's wrong here will not only solve my problem but also enlighten my understanding of the usage of self. Are there any tutorials about proper usage of self? I couldn't find anything beyond something like "self is the receiver of the message," which I didn't help me at all.

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  • How do I call a variable from another class?

    - by squeezemylime
    I have a class called 'Constants' that I am storing a String variable in. This class contains a few global variables used in my app. I want to be able to reference this class and call the variable (called profileId) in other Views of my app. I looked around and found a few examples, but am not sure how to do this. Currently my setup is: Constants.h @interface Constants : UIViewController { NSString *profileId; } @property (nonatomic, retain) NSString *profileId; @end Constants.m #import "Constants.h" @implementation Constants @synthesize profileId; - (void)dealloc { [profileId release]; [super dealloc]; } And I am trying to call the variable profileId in a new View via this way: NewView.h file @class Constants; NewView.m file NSLog(@"ProfileId is:", [myConstants profileId]); Is there something I'm missing? It is coming up null, even though I am properly storing a value in it in another function via this way: Constants *Constant; Constant = [[Constants alloc] init]; Constant.profileId = userId;

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  • Getting MAX_INT from NSDateComponents

    - by MattyW
    I'm trying to write my first iPhone app, and I'm using a date picker object for the user to enter their date of birth. Part of my app requires the year in int format. I've added the code as below. What's odd is that 'month' gets the right value. But day and year seem to be stuck at MAX_INT (2147483647). Can anyone tell me what I'm doing wrong? -(IBAction)dateOfBirthChanged:(id)sender { NSCalendar* calender = [NSCalendar currentCalendar]; NSDateComponents* dateComponents = [calender components:NSMonthCalendarUnit fromDate:[datepicker date]]; NSInteger day = [dateComponents day]; NSInteger month = [dateComponents month]; NSInteger year = [dateComponents year]; label.text = [NSString stringWithFormat:@"Your year of birth is %d", year]; }

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  • intialization with a nibFIle failed

    - by zp26
    Hi, I have a problem. I try to initialize a variabile in a classViewController created inside a xib file. I try with the code below but when i append a object to array, these array isn't initialized. Can you help me? thanks and sorry for my english. #import <UIKit/UIKit.h> @interface AccelerometroViewController : UIViewController <UIAccelerometerDelegate, UITextFieldDelegate, UIAlertViewDelegate>{ //..... NSMutableArray *arrayPosizioni; NSMutableArray *arrayPosizioniCorrenti; NSString *nomePosizioneCorrente; } -(IBAction)salvaPosizione; //... @property (nonatomic, assign) NSMutableArray *arrayPosizioni; @property (nonatomic, assign) NSMutableArray *arrayPosizioniCorrenti; @property (nonatomic, assign) NSString *nomePosizioneCorrente; @end #import "AccelerometroViewController.h" #import "Position.h" @implementation AccelerometroViewController float actualX; float actualY; float actualZ; @synthesize arrayPosition; @synthesize arrayCurrentPosition; @synthesize nameCurrentPosition; -(id)init { self = [super init]; if (self != nil) { arrayPosition = [[NSMutableArray alloc]init]; arrayCurrentPosition = [[NSMutableArray alloc]init]; nameCurrentPosition = [NSString stringWithFormat:@"noPosition"]; actualX = 0; actualY = 0; actualZ = 0; } return self; } -(void)updateTextView:(NSString*)nomePosizione { NSString *string = [NSString stringWithFormat:@"%@", nameCurrentPosition]; textEvent.text = [textEvent.text stringByAppendingString:@"\n"]; textEvent.text = [textEvent.text stringByAppendingString:string]; } -(IBAction)savePosition{ Posizione *newPosition; newPosition = [[Position alloc]init]; if([newPosition setValue:(NSString*)fieldNomePosizione.text:(float)actualX:(float)actualY:(float)actualZ]){ //setValue is a method of Position. I'm sure that this method is correct UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Salvataggio Posizione" message:@"Posizione salvata con successo" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil]; [alert show]; [alert release]; [arrayPosition addObject:newPosition]; } else{ UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Salvataggio osizione" message:@"Errore nel salvataggio" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil]; [alert show]; [alert release]; } } - (void) initialise { arrayPosition = [[NSMutableArray alloc] init]; arrayCurrentPosition = [[NSMutableArray alloc] init]; nameCurrentPosition = @"noPosition"; actualX = 0; actualY = 0; actualZ = 0; } - (id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)nibBundle { if (self = [super initWithNibName:nibName bundle:bundle]) { [self initialise]; } }

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  • Reducing lag when downloading large amount of data from webpage

    - by Mahir
    I am getting data via RSS feeds and displaying each article in a table view cell. Each cell has an image view, set to a default image. If the page has an image, the image is to be replaced with the image from the article. As of now, each cell downloads the source code from the web page, causing the app to lag when I push the view controller and when I try scrolling. Here is what I have in the cellForRowAtIndexPath: method. NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"]; storyLink = [storyLink stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *sourceCode = [NSString stringWithContentsOfURL:[NSURL URLWithString:storyLink] encoding:NSUTF8StringEncoding error:&error]; NSString *startPt = @"instant-gallery"; NSString *startPt2 = @"<img src=\""; if ([sourceCode rangeOfString:startPt].length != 0) { //webpage has images // find the first "<img src=...>" tag starting from "instant-gallery" NSString *trimmedSource = [sourceCode substringFromIndex:NSMaxRange([sourceCode rangeOfString:startPt])]; trimmedSource = [trimmedSource substringFromIndex:NSMaxRange([trimmedSource rangeOfString:startPt2])]; trimmedSource = [trimmedSource substringToIndex:[trimmedSource rangeOfString:@"\""].location]; NSURL *url = [NSURL URLWithString:trimmedSource]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *image = [UIImage imageWithData:data]; cell.picture.image = image; Someone suggested using NSOperationQueue. Would this way be a good solution? EDIT: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *MyIdentifier = @"FeedCell"; LMU_LAL_FeedCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier]; if (cell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"LMU_LAL_FeedCell" owner:self options:nil]; cell = (LMU_LAL_FeedCell*) [nib objectAtIndex:0]; } int storyIndex = [indexPath indexAtPosition: [indexPath length] - 1]; NSString *untrimmedTitle = [[stories objectAtIndex: storyIndex] objectForKey: @"title"]; cell.title.text = [untrimmedTitle stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; CGSize maximumLabelSize = CGSizeMake(205,9999); CGSize expectedLabelSize = [cell.title.text sizeWithFont:cell.title.font constrainedToSize:maximumLabelSize]; //adjust the label to the the new height. CGRect newFrame = cell.title.frame; newFrame.size.height = expectedLabelSize.height; cell.title.frame = newFrame; //position frame of date label CGRect dateNewFrame = cell.date.frame; dateNewFrame.origin.y = cell.title.frame.origin.y + cell.title.frame.size.height + 1; cell.date.frame = dateNewFrame; cell.date.text = [self formatDateAtIndex:storyIndex]; dispatch_queue_t someQueue = dispatch_queue_create("cell background queue", NULL); dispatch_async(someQueue, ^(void){ NSError *error = nil; NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"]; storyLink = [storyLink stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *sourceCode = [NSString stringWithContentsOfURL:[NSURL URLWithString:storyLink] encoding:NSUTF8StringEncoding error:&error]; NSString *startPt = @"instant-gallery"; NSString *startPt2 = @"<img src=\""; if ([sourceCode rangeOfString:startPt].length != 0) { //webpage has images // find the first "<img src=...>" tag starting from "instant-gallery" NSString *trimmedSource = [sourceCode substringFromIndex:NSMaxRange([sourceCode rangeOfString:startPt])]; trimmedSource = [trimmedSource substringFromIndex:NSMaxRange([trimmedSource rangeOfString:startPt2])]; trimmedSource = [trimmedSource substringToIndex:[trimmedSource rangeOfString:@"\""].location]; NSURL *url = [NSURL URLWithString:trimmedSource]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *image = [UIImage imageWithData:data]; dispatch_async(dispatch_get_main_queue(), ^(void){ cell.picture.image = image; }); }) //error: expected expression } return cell; //error: expected identifier } //error extraneous closing brace

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  • NSPredicate aggregate function [SIZE] gives 'unsupported function expression' error

    - by jinglesthula
    iOS 4: I have entities in Core Data (using SQLite, which is a requirement) of: Request Response (which has a property personId) Revision Relationships are: Request <-- Revision Request <-- Response Revision <-- Response (e.g. each request may have many responses; each request/response pair may have many revisions) I'm trying to do a predicate to get all Responses with a given personId that have zero Revisions. Using: (personId == %d) && (Request.Revision[SIZE] == 0) in my predicate string gives me a runtime exception "Unsupported function expression Request.Revision[SIZE]" The documentation seems pretty sparse on aggregate functions, only noting that they exist, but with no syntax or examples. Not sure if it's my syntax or if the SIZE function really isn't supported in iOS.

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  • UITabBarController not showing all view controllers

    - by rounak
    My UITabBarcontroller has two view controllers -Favorites -Keypad I add these two controllers in an array in the order Favorites,Keypad,nil. When the app is launched only the Favorites tab appears in the tabbar, I have to click the second tab for the "Keypad" (Title of the viewController) text to appear on the tabbar. How do I make the tabbar have the title of both the view controllers at startup itself?

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  • ios - how do I concatinate strings to create a url?

    - by GeekedOut
    I am trying to make a url by first collecting the parameters, and then in one statement creating the actual url. Here is what I am trying to do: NSString *urlString = @"http://www.some_login_url.com?email=%@&password=%@"; NSString *email = self.email.text; NSString *password = self.password.text; NSString *url_to_send = [NSString stringWithFormat:@"%@%@", urlString , email , password]; So what I wanted to do was replace the @ symbols with the values in the variables, but instead the second variable just got appended to the end of the string. How would I change the last line so I could put the right parameters in their correct spots? Thanks!!

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  • FJSTransitionController setup and use in View Controller not main app delegate

    - by elliotrock
    I am trying to set up Corey Floyd's FJSTransitionController. My app uses a main view controller to manage the main view navigation. I also went through the source to fix it for ARC. Followed instructions and in my main delegate .h I have in the usual spots: FJTransitionController* mainTransitionController; @property (nonatomic,retain) FJTransitionController* mainTransitionController; delegate .m has the following @synthesize mainTransitionController And in the - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions mainTransitionController=[[FJTransitionController alloc] init]; // do I need to instantise? [self.window addSubview:mainTransitionController.view]; [mainTransitionController setViewControllerClass:[[mainViewController sendMissionsPanelViewController] class] forKey:@"missionView"]; The last line is complaining that there is no @interface for FJTransitionController? Any help please.

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  • ios - almost there with updating Core Data

    - by Jeff Kranenburg
    I have been following the answer of this question: How to update existing object in core data? and in the answer it comes across this line of code to update a record within the array: Favorits* favoritsGrabbed = [results objectAtIndex:0]; Now this updates whatever is set a record 0 of the database, no matter what cell I select to edit. I am sorry but I cannot figure out how to change it into updating the cell I have selected. Starting to grow grey hairs here:-) The problem (maybe it is my mindset) is that I am required to give an integer and I am unable to find something to substitute it. Any help would be great.

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  • Creation of model in core data on the fly

    - by user1740045
    How can we create a model in core data on the fly? I.e getting the schema of database from somewhere and then creating a Core Data Object graph? *QuesTion:* Yes thats fine, agreed with all the advantages. But, can anybody can tell practically, what is the benefit of integrating Core Data into project instead of using SQL directly. 1.No need to write SQL boiler plate code [but need to learn Core Data Model (steep curve)] 2.WE can undo and redo changes [but practically who needs it] 3.we can migrate to another schema [that can be done by SQLite as well jus need to add another field into table] 4.For say aggregation on some field in table,in Core Data we need to loop through Core Data Objects whereas in SQLite we need to first write SQLite Boiler Plate Code and then the basic aggregation SQL query,which is easy to write,only length of code will increase...But in case of Core Data (need to learn a lot). So apart from reducing the length of Code,does it actually adds value to project? or in terms of Memory Efficiency,Performance,etc.. PS: If anybody has actualy worked on Core Data(Model Creation On the Fly) , if possible share and gve pointers..thanks!

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  • NSString cannot be released

    - by Stanley
    Consider the following method and the caller code block. The method analyses a NSString and extracts a "http://" string which it passes out by reference as an auto release object. Without releasing g_scan_result, the program works as expected. But according to non-arc rules, g_scan_result should be released since a retain has been called against it. My question are : Why g_scan_result cannot be released ? Is there anything wrong the way g_scan_result is handled in the posted coding below ? Is it safe not to release g_scan_result as long as the program runs correctly and the XCode Memory Leak tool does not show leakage ? Which XCode profile tools should I look into to check and under which subtitle ? Hope somebody knowledgeable could help. - (long) analyse_scan_result :(NSString *)scan_result target_url :(NSString **)targ_url { NSLog (@" RES analyse string : %@", scan_result); NSRange range = [scan_result rangeOfString:@"http://" options:NSCaseInsensitiveSearch]; if (range.location == NSNotFound) { *targ_url = @""; NSLog(@"fnd string not found"); return 0; } NSString *sub_string = [scan_result substringFromIndex : range.location]; range = [sub_string rangeOfString : @" "]; if (range.location != NSNotFound) { sub_string = [sub_string substringToIndex : range.location]; } NSLog(@" FND sub_string = %@", sub_string); *targ_url = sub_string; return [*targ_url length]; } The following is the caller code block, also note that g_scan_result has been declared and initialized (on another source file) as : NSString *g_scan_result = nil; Please do send a comment or answer if you have suggestions or find possible errors in code posted here (or above). Xcode memory tools does not seem to show any memory leak. But it may be because I do not know where to look as am new to the memory tools. { long url_leng = [self analyse_scan_result:result target_url:&targ_url]; NSLog(@" TAR target_url = %@", targ_url); UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Scanned Result" message:result delegate:g_alert_view_delegate cancelButtonTitle:@"OK" otherButtonTitles:nil]; if (url_leng) { // ****** The 3 commented off statements // ****** cannot be added without causing // ****** a crash after a few scan result // ****** cycles. // ****** NSString *t_url; if (g_system_status.language_code == 0) [alert addButtonWithTitle : @"Open"]; else if (g_system_status.language_code == 1) [alert addButtonWithTitle : @"Abrir"]; else [alert addButtonWithTitle : @"Open"]; // ****** t_url = g_scan_result; g_scan_result = [targ_url retain]; // ****** [t_url release]; } targ_url = nil; [alert show]; [alert release]; [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:@selector(activate_qr_scanner:) userInfo:nil repeats:NO ]; return; }

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  • Not found in protocol

    - by Alex
    I've subclassed MKAnnotation so that i can assign objects to annotations and then assign this object to a view controller like so: - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control { PlaceDetailView *detailView = [[PlaceDetailView alloc] initWithStyle:UITableViewStyleGrouped]; detailView.place = [view.annotation place]; [self.navigationController pushViewController:detailView animated:YES]; [detailView release]; } This is working great but i'm having the following issues: If i try and access the place getter method like so view.annotation.place i recieve an error: Accessing unknown place getter method If i acces the place getter method like so [view.annotation place] i receive a warning: place not found in protocol From my understanding this is because the place object is not defined in the MKAnnotation protocol, although i'm aware of this i'm not sure how to tell the complier that place does exist and it's not calling it blind.

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  • UINavigationController shows blank view

    - by Adam8797
    I am making a simple navigation based application that drills down one level and show a new xib file each time. When I drill down one level my screen shows up blank. I still have the navigation controller at the top with a back button but my view dosent load. Here is my code - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { circle_area *subViewOneController = [[circle_area alloc] init]; UIViewController *tvc = subViewOneController; if (indexPath.row == 0 && indexPath.section == 0) { [[self navigationController] pushViewController:tvc animated:YES]; } } like I said this returns a blank screen.

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  • sending image in a faceless email

    - by anurag
    I am trying to send a faceless(without showing the interface)email by using the code below: I also want to attach an image to this email can anybody suggest is it possible??? (void) sendEmailTo:(NSString *)toStr withSubject:(NSString *)subjectStr withBody:(NSString *)bodyStr { NSString *emailString=[[NSString alloc] initWithFormat:@"mailto:?to=%@&subject=%@&body=%@", [toStr stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding], [subjectStr stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding], [bodyStr stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding]]; [[UIApplication sharedApplication] openURL:[NSURL URLWithString:emailString]]; [emailString release]; }

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  • What's safe to assume about the NSMutableArray / NSArray class cluster?

    - by andyvn22
    I know you shouldn't use this to decide whether or not to change an array: if ([possiblyMutable isKindOfClass:[NSMutableArray class]]) But say I'm writing a method and need to return either an NSMutableArray or an NSArray, depending on the mutability of possiblyMutable. The class using my method already knows whether or not it's acceptable to change the returned array. Whether or not it's acceptable to change the returned array directly correlates with whether or not it's acceptable to change possiblyMutable. In that specific case, is this code safe? It seems to me that if it's not acceptable to change the array, but we accidentally get a mutable array, it's ok, because the class using my method won't try to change it. And if it is acceptable to change the array, then we will always get possiblyMutable as an NSMutableArray (though this is the part I'm not entirely clear on). So... safe or not? Alternatives?

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  • How can I get a nstableview to send an action when the user double-clicks an editable cell

    - by overcyn
    I am trying to emulate the behavior found in finder and itunes. Single click on a selected object edits it. Double click opens the object. I have set the doubleAction of the tableView but like it says in the documentation. "If the double-clicked cell is editable, this message isn’t sent and the cell is edited instead." I dont want this. Is there a way i can get that message sent even if the cell is editable? I really have no idea how to begin implementing this. Any general pointers would be appreciated.

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  • Do we need to release an UIImage object even not allocated memory?

    - by Madan Mohan
    Hi Guys, I added an image to button UIImage* deleteImage = [UIImage imageNamed:@"Delete.png"]; CGRect imageFrame=CGRectMake(-4,-4, 310, 55); [btn setFrame:imageFrame]; btn.backgroundColor=[UIColor clearColor]; [btn setBackgroundImage:deleteImage forState:UIControlStateNormal]; [btn setTitle:@"Delete" forState:UIControlStateNormal]; [btn addTarget:self action:@selector(editDeleteAction) forControlEvents:UIControlEventTouchUpInside]; [elementView addSubview:btn]; [deleteImage release];// do we need to release the image here If I release here its working fine but in object allocations no.of image count is increasing.

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