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POMemory management in viewDidUnload - should I nil both array and objects inside?
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copied!<p>I have a tableview to load news from internet. I and trying to nil all properties in viewDidUnload.</p> <pre><code>- (void)viewDidUnload { self.newsArray = nil; self.newsTableView = nil; self.indicatorView = nil; // self.iconDownLoader = nil; self.downloadArray = nil; [super viewDidUnload]; } </code></pre> <p>Every time the app crash in viewDidUnload. If I comment self.iconDownLoader = nil;, it will be fine. So can any one tell me why does this happen? Thanks you.</p> <p><strong>---------------------NewsViewController.m--------------------------</strong></p> <pre><code>// // NewsViewController.m // // Created by on 18/01/12. // Copyright (c) 2012 __MyCompanyName__. All rights reserved. // #import "NewsViewController.h" #import "ASIHTTPRequest.h" #import "SBJson.h" #import "NewsModel.h" #import "NewsDetailViewController.h" #define kCustomRowCount 6 #define IconPlaceHolder @"Spinner" @implementation NewsViewController @synthesize appDelegate, newsTableViewCell, newsTableView, indicatorView; @synthesize iconDownLoader, newsArray, downloadArray; - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { // setup appDelegate self.appDelegate = (SydneyAppDelegate *)[[UIApplication sharedApplication] delegate]; // initial arrays self.newsArray = [[NSMutableArray alloc] init]; self.downloadArray = [[NSMutableArray alloc] init]; } return self; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; } #pragma mark - View lifecycle - (void)viewDidLoad { [super viewDidLoad]; if(self.appDelegate.reachable) { [self getNews]; } else { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"No Connection" message:@"No Internet connection. Please try again later." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; } } - (void)viewDidUnload { self.newsArray = nil; self.newsTableView = nil; self.indicatorView = nil; // self.iconDownLoader = nil; self.downloadArray = nil; [super viewDidUnload]; } #pragma mark - ASIHTTPRequest - (void) getNews { NSURL *url = [NSURL URLWithString:@"http://ferrarimaseratisydney.com/api/getPublicNews.html"]; ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url]; [request setDelegate:self]; [request startAsynchronous]; } - (void) requestFinished:(ASIHTTPRequest *)request { NSString *responseString = [request responseString]; NSArray *json = [responseString JSONValue]; for (id aNewsInJson in json) { NewsModel *aNews = [[NewsModel alloc] initWithJson:aNewsInJson]; [self.newsArray addObject:aNews]; } [self.indicatorView removeFromSuperview]; [self.newsTableView reloadData]; } - (void) requestFailed:(ASIHTTPRequest *)request { NSError *error; error = [request error]; } #pragma mark - Table view delegate - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { [tableView deselectRowAtIndexPath:indexPath animated:YES]; // Navigation logic may go here. Create and push another view controller. NewsDetailViewController *newsDetailViewController = [[NewsDetailViewController alloc] init]; // transform news array newsDetailViewController.news = [self.newsArray objectAtIndex:indexPath.row]; // Pass the selected object to the new view controller. [self.navigationController pushViewController:newsDetailViewController animated:YES]; } #pragma mark - Table view data source - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [self.newsArray count]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"NewsCellIdentifier"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { [[NSBundle mainBundle] loadNibNamed:@"NewsTableViewCell" owner:self options:nil]; cell = self.newsTableViewCell; self.newsTableViewCell = nil; } // read from newsModel NewsModel *news = [self.newsArray objectAtIndex:indexPath.row]; UILabel *label; label = (UILabel *)[cell viewWithTag:10]; label.text = [NSString stringWithString:news.title]; label = nil; label = (UILabel *)[cell viewWithTag:11]; label.text = [NSString stringWithString:news.description]; UIImageView *imageView = (UIImageView *)[cell viewWithTag:12]; imageView.image = news.image; if (news.image == nil) { imageView.image = [UIImage imageNamed:IconPlaceHolder]; self.iconDownLoader = [[IconDownLoader alloc] init]; self.iconDownLoader.url = news.imageUrl; self.iconDownLoader.delegate = self; self.iconDownLoader.indexPath = indexPath; if (self.appDelegate.ip4 == YES) { self.iconDownLoader.width = 300; self.iconDownLoader.height = 150; } else { self.iconDownLoader.width = 150; self.iconDownLoader.height = 75; } [self.downloadArray addObject:self.iconDownLoader]; [self.iconDownLoader start]; } return cell; } #pragma mark - IconDownLoaderDelegate - (void)iconDownLoadFinsh:(NSData *)imageData row:(NSIndexPath *)indexPath { UITableViewCell *cell = [self.newsTableView cellForRowAtIndexPath:indexPath]; UIImageView *imageView = (UIImageView *)[cell viewWithTag:12]; if (imageData != 0) { imageView.image = [UIImage imageWithData:imageData]; } else { imageView.image = [UIImage imageNamed:@"icon57"]; } NewsModel *newsModel = [self.newsArray objectAtIndex:indexPath.row]; newsModel.image = [UIImage imageWithData:imageData]; } @end </code></pre> <p><strong>-----------------------IconDownLoader.m-------------------</strong></p> <pre><code>// // IconDownLoader.m // // Created by on 24/11/11. // Copyright (c) 2011 __MyCompanyName__. All rights reserved. // #import "IconDownLoader.h" #import "ASIHTTPRequest.h" @implementation IconDownLoader @synthesize delegate = _delegate; @synthesize url = _url; @synthesize indexPath = _indexPath; @synthesize width = _width; @synthesize height = _height; @synthesize request = _request; - (void)start { NSString *originalString = @"width=%s&height=%s"; NSString *newString = [NSString stringWithFormat:@"width=%d&height=%d&type=jpg", self.width, self.height]; NSString *resizedURL = [self.url stringByReplacingOccurrencesOfString:originalString withString:newString]; NSURL *url = [NSURL URLWithString:[resizedURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]; _request = [ASIHTTPRequest requestWithURL:url]; if (_indexPath) { _request.userInfo = [NSDictionary dictionaryWithObject:_indexPath forKey:@"indexPath"]; } [_request setDelegate:self]; [_request startAsynchronous]; } - (void)requestFinished:(ASIHTTPRequest *)request { NSInteger statusCode = request.responseStatusCode; switch (statusCode) { case 401: // Not Authorized: either you need to provide authentication credentials, or the credentials provided aren't valid. break; case 200: { NSData *responseData = [request responseData]; if (!responseData) { UIAlertView *alertView; alertView = [[UIAlertView alloc] initWithTitle:@"Oops" message:[NSString stringWithFormat:@"Download failed in row %d", _indexPath.row] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; return; } [_delegate iconDownLoadFinsh:responseData row:[request.userInfo objectForKey:@"indexPath"]]; } break; default:{ } } } - (void)dealloc { if (_request != nil) { [_request clearDelegatesAndCancel]; } } @end </code></pre>

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