我有一个tableview来加载来自互联网的新闻。我试图在viewDidUnload中删除所有属性。
- (void)viewDidUnload
{
self.newsArray = nil;
self.newsTableView = nil;
self.indicatorView = nil;
// self.iconDownLoader = nil;
self.downloadArray = nil;
[super viewDidUnload];
}
每次应用程序在viewDidUnload中崩溃。如果我评论self.iconDownLoader = nil;，那就没问题。所以任何人都可以告诉我为什么会这样？谢谢你。
--------------------- NewsViewController.m -------------------- ------
//
// 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
----------------------- IconDownLoader.m ------------------ -
//
// 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
答案 0 :(得分：1)
这里没有足够的信息告诉你，但是你可能直接在我们看不到的代码的其他部分发布了iconDownloader而没有在那时设置对nil的引用。
然后在viewDidUnload中，您尝试释放无效的引用。
对于@synthesize，请使用：
@synthesize iconDownLoader = _iconDownloader;
然后修复所有编译器警告以使用self.icondownloder而不是iconDownloader，并消除“release”的所有用法（假设你的属性被标记为保留它应该是）。
事实上，也许你的整个问题是该属性不是一个保留属性，所以你创建了iconDOwnloader并且它会被及时释放。
答案 1 :(得分：1)
通常在viewDidUnload中，您应该只释放和归零所有对您拥有的nib对象的引用。
也就是说，如果消耗大量内存，也可以销毁viewDidUnload中的模型对象。您应该记住viewDidUnload是viewDidLoad的对应物，因此一个好的经验法则是仅销毁您在viewDidUnload中创建的viewDidLoad中的对象。您还应该记住，当视图控制器被释放时，viewDidUnload 不被调用 - 只有当它的视图是。
在您的情况下，我不会仅仅因为您在newsArray中创建downloadArray和init...而发布removeAllObjects和{{1}}。我只会发送{{1}}代替。
对于崩溃，每次单元格需要图像时都会创建一个新的共享图标下载器，这有点尴尬。如果确实需要共享的下载程序实例，则不应为每个单元格重新创建它。看起来你想要保留你在ivar数组中创建的所有下载器，因为每个下载器都是一次性的，并且负责加载单个图像。