I'm implementing asynchronous image loading in UITableView, If I scroll rows fast my app crashes due to message sent to zombie... What is wrong am I doing here?
//loading image from URL
-(void)loadImageFromURL:(NSURL*)url {
if (connection!=nil) { [connection release]; }
//data is NSMutableData
if (data!=nil) { [data release]; }
NSURLRequest* request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
}
//Append received data when it is received
- (void)connection:(NSURLConnection *)theConnection didReceiveData:(NSData *)incrementalData {
if (data==nil) { data = [[NSMutableData alloc] init]; }
[data appendData:incrementalData]; //Message sent to zombie, app CRASHES HERE
}
//When finished
- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection {
//so self data now has the complete image
[connection release];
connection=nil;
//Use received data to construct image
[data release];
data=nil;
}
Here:
if (connection!=nil) { [connection release]; }
if (data!=nil) { [data release]; }
you are releasing the data. Later you try using the released data so it crashes. Try this:
if (connection!=nil) { [connection release]; connection = nil; }
if (data!=nil) { [data release]; data = nil; }
That way your if statements will actually trigger.
Related
I'm an iPhone developer.
I studied about how to use NSThread. So I created source code.
But, I'm not sure about my source code whether good or bad.
-(void)check_threadEnd
{
if ([_thread isFinished]) {
threadCount++;
if (threadCount == 4) {
[self performSelector:#selector(removeActivityView) withObject:nil afterDelay:0.0];
[self.tableView reloadData];
}
}
}
Sometimes, threadCount doesn't become 4.
So, ActiveView is worked continual without stopping.
Turn the timer after a period of time, remove ActiveView?
I'll give you some advice please.
-(IBAction)click_ServerSync:(id)sender
{
if ([util checkNetwork]) {
threadCount = 0 ;
[self displayActivityView];
NSOperationQueue *queue = [[[NSOperationQueue alloc] init] autorelease];
[queue setMaxConcurrentOperationCount:4];
_thread = [[NSThread alloc] initWithTarget:self selector:#selector(_th) object:nil];
[_thread start];
}
}
-(void)_th
{
[self performSelectorOnMainThread:#selector(LoadXml:) withObject:#"XML1" waitUntilDone:NO];
[self performSelectorOnMainThread:#selector(LoadXml:) withObject:#"XML2" waitUntilDone:NO];
[self performSelectorOnMainThread:#selector(LoadXml:) withObject:#"XML3" waitUntilDone:NO];
[self performSelectorOnMainThread:#selector(LoadXml:) withObject:#"XML4" waitUntilDone:NO];
}
-(void)LoadXml:(NSString*)P_VAL
{
NSString *smsURL = [NSString stringWithFormat:#"%#%#.asp", XML_URL, P_VAL];
NSString *sendAuthInfo = [NSString stringWithFormat:#"A=%#&B=%d&C=%#&D=%#" , A, B, C, D ];
NSString *val = [sendAuthInfo stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSMutableURLRequest *request = [[[NSMutableURLRequest alloc]initWithURL:[NSURL URLWithString:smsURL]]autorelease];
[request setURL:[NSURL URLWithString:smsURL]];
[request setHTTPMethod:#"POST"];
[request setHTTPBody: [val dataUsingEncoding: NSUTF8StringEncoding]];
[self startAsyncLoad:request tag:P_VAL];
}
- (void)startAsyncLoad:(NSMutableURLRequest*)request tag:(NSString*)tag {
CustomURLConnection *connection = [[CustomURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES tag:tag];
if (connection) {
[receivedData setObject:[[NSMutableData data] retain] forKey:connection.tag];
}
}
- (NSMutableData*)dataForConnection:(CustomURLConnection*)connection {
NSMutableData *data = [receivedData objectForKey:connection.tag];
return data;
}
-(void)check_threadEnd
{
if ([_thread isFinished]) {
threadCount++;
if (threadCount == 4) {
[self performSelector:#selector(removeActivityView) withObject:nil afterDelay:0.0];
[self.tableView reloadData];
}
}
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
NSMutableData *dataForConnection = [self dataForConnection:(CustomURLConnection*)connection];
[dataForConnection setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
NSMutableData *dataForConnection = [self dataForConnection:(CustomURLConnection*)connection];
[dataForConnection appendData:data];
}
-(void)connectionDidFinishLoading:(NSURLConnection*)connection
{
NSLog(#" connection connectionDidFinishLoading : %d", [connection retainCount]);
NSMutableData *dataForConnection = [self dataForConnection:(CustomURLConnection*)connection];
[connection release];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
NSXMLParser *xmlParser = [[[NSXMLParser alloc] initWithData:dataForConnection] autorelease];
XMLParser *parser = [[XMLParser alloc] initXMLParser];
[xmlParser setDelegate:(id)parser];
parser.viewDelegate = (id)self;
[xmlParser parse]; // xml parser
}
Do you have a reason as to why you are opting for NSThread over NSOperation? NSOperation abstracts away a lot of the lower-level thing you would have to worry about with NSThread. I would strongly recommend you read up on this concurrency programming guide from Apple.
Pay attention to the last section, Migrating Away From Threads, as it talks about additional alternatives that can help you write robust, clean code.
I need to make multiple NSURLConnections to a JSON Web Service. I would like each WS call to keep in UI informed, probably with a UIActivityIndicatorView and label. So far I've created a NSURLConnection helper class to handle the connection and placed the URL delegates in the View. This works great for updating the UI with a single WS call.
For multiple calls, I'm trying to use an NSOperationQueue. I'd like to setMaxConcurrentOperationCount to one on the queue so that each Operation executes one at a time. Here's the relevant code on my View Controller:
ViewController.m
#import "URLOperationHelper.h"
#implementation ViewController
- (IBAction)showPopup:(id)sender
{
// Dictonary holds POST values
NSMutableDictionary *reqDic = [NSMutableDictionary dictionary];
// Populate POST key/value pairs
[reqDic setObject:#"pw" forKey:#"Password"];
[reqDic setObject:#"ur" forKey:#"UserName"];
operationQueue = [[NSOperationQueue alloc] init];
[operationQueue setMaxConcurrentOperationCount:1];
[operationQueue cancelAllOperations];
[operationQueue setSuspended:YES];
URLOperationHelper *wsCall1 = [[URLOperationHelper alloc] initWithURL:#"urlString1" postParameters:reqDic urlDelegate:self];
URLOperationHelper *wsCall2 = [[URLOperationHelper alloc] initWithURL:#"urlString2" postParameters:reqDic urlDelegate:self];
[operationQueue addOperation:wsCall1];
[operationQueue addOperation:wsCall2];
}
// Did the URL Connection receive a response
-(void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
NSLog(#"Did receive response: %#", response);
NSHTTPURLResponse* httpResponse = (NSHTTPURLResponse*)response;
int code = [httpResponse statusCode];
// Handle status code here
webData = [[NSMutableData alloc]init];
}
// Did the URL Connection receive data
-(void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSLog(#"Did receive data: %#", [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
assert(webData != nil);
[webData appendData:data];
}
// Did the connection fail with an error?
-(void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
NSLog(#"%#", error);
}
// Executes after a successful connection and data download
-(void) connectionDidFinishLoading:(NSURLConnection *)connection
{
NSLog(#"Connection finished");
}
#end
And here is my URLOperationHelper.m
#implementation URLHelper
- (id)initWithURL:(NSString *)urlPath
postParameters:(NSMutableDictionary *)postParameters
urlParentDelegate:(id) pDelegate
{
if(self = [super init])
{
connectionURL = urlPath;
postParams = postParameters;
parentDelegate = pDelegate;
}
return self;
}
- (void)done
{
// Cancel the connection if present
if(urlConnection)
{
[urlConnection cancel];
urlConnection = nil;
}
// Alert
[self willChangeValueForKey:#"isExecuting"];
[self willChangeValueForKey:#"isFinished"];
executing = NO;
finished = YES;
[self willChangeValueForKey:#"isFinished"];
[self willChangeValueForKey:#"isExecuting"];
}
- (void)cancel
{
// Possibly add an NSError Property
[self done];
}
- (void)start
{
// Make sure this operation starts on the main thread
if(![NSThread isMainThread])
{
[self performSelectorOnMainThread:#selector(start) withObject:nil waitUntilDone:NO];
return;
}
// Make sure that the operation executes
if(finished || [self isCancelled])
{
[self done];
return;
}
[self willChangeValueForKey:#"isExecuting"];
executing = YES;
[self main];
[self willChangeValueForKey:#"isExecuting"];
}
- (void)main
{
NSError *error = nil;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:postParams options:NSJSONWritingPrettyPrinted error:&error];
// Convert dictionary to JSON
NSString *requestJSON = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
NSLog(#"JSONRequest: %#", requestJSON);
// Declare Webservice URL, request, and return data
url = [[NSURL alloc] initWithString:connectionURL];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
NSData *requestData = [NSData dataWithBytes:[requestJSON UTF8String] length:[requestJSON length]];
// Build the request
[request setHTTPMethod:#"POST"];
[request setValue:[NSString stringWithFormat:#"%d", [requestData length]] forHTTPHeaderField:#"Content-Length"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:requestData];
// Connect to Webservice
// Responses are handled in the delegates below
urlConnection = [[NSURLConnection alloc] initWithRequest:request delegate:parentDelegate startImmediately:YES];
}
- (BOOL)isConcurrent
{
return YES;
}
- (BOOL)isExecuting
{
return executing;
}
-(BOOL)isFinished
{
return finished;
}
#end
The problem that I'm having is the Start method for the URLOperation is never called. The OperationQueue is created and the Operations are called, but nothing happens after that, execution or thread wise.
Also, is this a correct line of thinking to provide UI feedback using NSOperationQueues like this? I.E. calling the NSURLDelegates from the Operation?
If you set setSuspended to YES before adding the Operations then your Operations will be queued into a suspended queue.. i suggest not to suspend the queue at
furthermore, your operation never ends anyway. You need to assign the operation itself as the delegate and implement all necessary delegate methods. In these methods you can forward the messages to your parentDelegate and decide when you are finished and call your done method when appropriate (i suggest connection:didFailWithError: and connectionDidFinishLoading:)
There is a good tutorial here: http://blog.9mmedia.com/?p=549
You are also not completely implementing key-value-coding compilant properties correct. Whenever you call willChangeValueForKey: you also need to call didChangeValueForKey afterwards:
- (void)start
{
...
[self willChangeValueForKey:#"isExecuting"];
executing = YES;
[self didChangeValueForKey:#"isExecuting"];
[self main];
}
and:
- (void)done
{
...
// Alert
[self willChangeValueForKey:#"isExecuting"];
[self willChangeValueForKey:#"isFinished"];
executing = NO;
finished = YES;
[self didChangeValueForKey:#"isFinished"];
[self didChangeValueForKey:#"isExecuting"];
}
See this Q/A for KVC: when to use "willChangeValueForKey" and "didChangeValueForKey"?
I want to create two connections in a single view controller class. I am using NSOperationQueue for this purpose. The two connections are created in two functions and push inside the queue .The problem is delegates are not called. Please help me out. Thanks you in advance
- (void)viewDidLoad {
[super viewDidLoad];
NSOperationQueue *queue=[[NSOperationQueue alloc] init];
NSInvocationOperation *invOperation1 = [[NSInvocationOperation alloc] initWithTarget:self selector:#selector(createConnection1) object:nil];
NSInvocationOperation *invOperation2 = [[NSInvocationOperation alloc] initWithTarget:self selector:#selector(createConnection2) object:nil];
NSArray *ops=[[NSArray alloc] initWithObjects:invOperation1,invOperation2,nil];
[queue addOperations:ops waitUntilFinished:YES];
}
-(void) createConnection1{
//create connection
NSLog(#"Create Connection 1");
url1 =[[NSMutableString alloc] initWithFormat:#"http://www.google.com/ig/api?weather=New Delhi"];
NSURLRequest *theRequest1=[NSURLRequest requestWithURL:[NSURL URLWithString:url1]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
theConnection1=[[NSURLConnection alloc] initWithRequest:theRequest1 delegate:self];
if (theConnection1) {
connectionCreated1=YES;
receivedData1 = [[NSMutableData data] retain];
NSLog(#"received data 1 %#",receivedData1);
//[theConnection1 setDelegate:self];
}
}
-(void) createConnection2{
//create connection
NSLog(#"Create Connection 2");
url2 =[[NSMutableString alloc] initWithFormat:#"http://www.google.com/ig/api?weather=Chennai"];
NSURLRequest *theRequest2=[NSURLRequest requestWithURL:[NSURL URLWithString:url2]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
theConnection2=[[NSURLConnection alloc] initWithRequest:theRequest2 delegate:self];
if (theConnection2) {
connectionCreated2=YES;
receivedData2 = [[NSMutableData data] retain];
//[theConnection2 setDelegate:self];
NSLog(#"received data 2 %#",receivedData2);
}
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
if (connectionCreated1==YES) {
[receivedData1 setLength:0];
}
else if (connectionCreated2==YES) {
[receivedData2 setLength:0];
}
else {
NSLog(#"did not receive response");
}
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
if (connectionCreated1==YES) {
[theConnection1 release];
xmlParser1 = [[NSXMLParser alloc] initWithData:receivedData1];
[xmlParser1 setDelegate:self];
[xmlParser1 parse];
}
else if(connectionCreated2==YES){
[theConnection2 release];
xmlParser2 = [[NSXMLParser alloc] initWithData:receivedData2];
[xmlParser2 setDelegate:self];
[xmlParser2 parse];
}
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"connection failed" message:#"" delegate:self cancelButtonTitle:#"ok" otherButtonTitles:nil];
[alert show];
[alert release];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
if (connectionCreated1==YES) {
[receivedData1 appendData:data];
}
else if(connectionCreated2==YES) {
[receivedData2 appendData:data];
}
else {
NSLog(#"data not received");
}
}
The URL you have given in the first link seems to be borken ... look at this "http://www.google.com/ig/api?weather=New Delhi".. there is space between new delhi. try this instead http://www.google.com/ig/api?weather=New+Delhi
I need to load data from my API without waiting 20s each time I launch my application.
So I use:
NSURL *myUrlCourses = [[NSURL alloc] initWithString:url];
NSMutableURLRequest *request = [NSURLRequest requestWithURL: myUrlCourses];
NSURLConnection *connexion = [[NSURLConnection alloc] initWithRequest:request delegate:self];
for my 10 first request in while loop which permit to get data in background.
But, when I get data from this request with:
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{}
The result don't match.
So, I think I have to use thread or something like that to get the right data for each request but I don't really know how!?
Could you help me to solve this problem?
Thanks
Store all of your connections in variables with describing names and then compare the pointer values.
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
if(connection == _theFacebookConnection)
{
//Handle Facebook code
}
else if(connection == _theTwitterConnection)
{
//Handle Twitter code
}
}
I use a CFMutableDictionaryRef to save another mutable dictionary for each connection. This inner dictionary can hold as much data as you want.
like this:
#interface Foo {
CFMutableDictionaryRef connections;
}
#implementation Foo
- (id)init {
self = [super init];
if (self) {
connections = CFDictionaryCreateMutable(kCFAllocatorDefault, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
}
return self;
}
- (BOOL)addURLRequest:(NSURLRequest *)request successSelector:(SEL)successSelector errorSelector:(SEL)errorSelector {
NSMutableDictionary *connectionInfo = [NSMutableDictionary dictionaryWithObjectsAndKeys:
[NSMutableData data], #"receivedData",
[NSValue valueWithPointer:successSelector], #"successSelector",
[NSValue valueWithPointer:errorSelector], #"errorSelector",
request, #"request",
nil];
NSURLConnection *connection = [[[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO] autorelease];
CFDictionaryAddValue(connections, connection, connectionInfo);
[connection start];
return YES;
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
NSMutableDictionary *connectionInfo = (NSMutableDictionary *)CFDictionaryGetValue(connections, connection);
[[connectionInfo objectForKey:#"receivedData"] appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
NSMutableDictionary *connectionInfo = (NSMutableDictionary *)CFDictionaryGetValue(connections, connection);
NSData *data = [connectionInfo objectForKey:#"receivedData"];
LogInfo(#"Finished Connection %#", connection);
SEL selector = [[connectionInfo objectForKey:#"successSelector"] pointerValue];
if ([self respondsToSelector:selector]) {
[self performSelector:selector withObject:data];
}
CFDictionaryRemoveValue(connections, connection);
}
I use ASIHTTPRequest for this sort of thing because I can use [request setUserInfo:(NSDictionary *)] to specify additional data that travels around with the request responses.
Then when I receive each response, I can look at that requests UserInfo dictionary and process the data accordingly.
What's nice about this is you can put as much or as little data into the UserInfo Dictionary as you require.
I'm newbie in Objective-C, and as most of the newbies I have a questions about references management.
I've written a class which downloads data using NSURLConnection. The code is similar to Apple's example in http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/URLLoadingSystem/Tasks/UsingNSURLConnection.html. The only difference is that receivedData variable is declared as "#property (nonatomic,retain) NSMutableData *receivedData;" In .m file I have "#synthesize receivedData = _receivedData;".
I have connectionStart function which starts downloading data. In this function I have this code:
if (theConnection) {
// Create the NSMutableData to hold the received data.
// receivedData is an instance variable declared elsewhere.
self.receivedData = [NSMutableData data];
} else {
// Inform the user that the connection failed.
}
The program crashes with this message:
2011-06-12 12:47:22.298 WebGallery[1212:207] *** -[NSConcreteMutableData release]: message sent to deallocated instance 0x118a6fe0
If I change receivedData assignment to this code:
self.receivedData = [[NSMutableData data] retain];
Then the program works correctly and no memory leaks are detected.
As you see I need to call retain on NSMutableData and I'm using property, which is declared as "retain".
Why does this happen?
EDIT: Full contents of .m file:
#import "GalleryData.h"
#import "XmlParser.h"
#implementation GalleryData
#synthesize receivedData = _receivedData;
#synthesize imagesData = _imagesData;
#synthesize delegate = _delegate;
#synthesize currentObjectType = _currentObjectType;
#synthesize currentObjectIndex = _currentObjectIndex;
- (id) init
{
[super init];
_imagesData = [[NSMutableArray alloc] init];
return self;
}
- (void) dealloc
{
[_imagesData release];
_imagesData = nil;
[super dealloc];
}
- (void) connectionStart:(NSURL *)theURL
{
NSURLRequest *theRequest = [NSURLRequest requestWithURL:theURL cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
if (theConnection) {
// Create the NSMutableData to hold the received data.
// receivedData is an instance variable declared elsewhere.
//ASK: Kodėl čia reikia daryti retain jei #property jau nustatyta retain?
self.receivedData = [[NSMutableData data] retain];
} else {
// Inform the user that the connection failed.
}
}
- (void) startLoading
{
NSLog(#"Loading started");
self.currentObjectIndex = 0;
self.currentObjectType = ObjectTypeXML;
[self connectionStart:[NSURL URLWithString:#"http://www.aleksandr.lt/gallery/data.xml"]];
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[self.receivedData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[self.receivedData appendData:data];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
[connection release];
[self.receivedData release];
NSLog(#"Connection failed! Error - %# %#",
[error localizedDescription],
[[error userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]);
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
[connection release];
if (self.currentObjectType == ObjectTypeXML) {
NSXMLParser *nsXmlParser = [[NSXMLParser alloc] initWithData:self.receivedData];
XmlParser *parser = [[XmlParser alloc] initXmlParser:self.imagesData];
[nsXmlParser setDelegate:parser];
[nsXmlParser parse];
[nsXmlParser release];
[parser release];
[self.receivedData release];
self.receivedData = nil;
if ([self.imagesData count]) {
self.currentObjectIndex = 0;
self.currentObjectType = ObjectTypeThumbImage;
ImageData *firstImage = [self.imagesData objectAtIndex:0];
NSURL *theURL = [NSURL URLWithString:firstImage.thumbImageURL];
[self connectionStart:theURL];
} else {
[self.delegate loadingFinished];
return;
}
} else if (self.currentObjectType == ObjectTypeThumbImage) {
ImageData *currentImage;
currentImage = [self.imagesData objectAtIndex:self.currentObjectIndex];
UIImage *thumbImage = [[UIImage alloc] initWithData:self.receivedData];
if (thumbImage == nil) {
NSLog(#"image was not created");
}
[currentImage setThumbImageScaled:thumbImage];
[thumbImage release];
[self.receivedData release];
self.receivedData = nil;
if (self.currentObjectIndex == ([self.imagesData count] - 1)) {
[self.delegate loadingFinished];
return;
}
self.currentObjectIndex++;
currentImage = [self.imagesData objectAtIndex:self.currentObjectIndex];
NSLog(#"'%#'", currentImage.thumbImageURL);
NSURL *theURL = [NSURL URLWithString:currentImage.thumbImageURL];
[self connectionStart:theURL];
}
}
#end
Do not call [self.receivedData release] - this leaves the internal pointer dangling. The whole point of a retained property is that it releases itself. Just do self.receivedData = nil.
Here is your problem:
[self.receivedData release];
self.receivedData = nil;
You're releasing the attribute twice (first time explicitly and second time implicitly by assigning nil).