I am using two objects i.e., pagesUrl and pagesXmlParser in the code and after their use, im releasing those two objects. Its running well but its showing them in memory leaks. when i tried to verify it, i checked the reference count of those objects and its showing '1' even after the objects are released. can any one help me out how to remove that leak and how to release those particular objects in the following code.
-(void)loadPagesForChapter:(NSString *)path{
// have to parse the pages xml for this chapter
NSURL *pagesUrl = [[NSURL alloc] initFileURLWithPath:[self pagesXmlPath:path]];
NSXMLParser *pagesXmlParser = [[NSXMLParser alloc] initWithContentsOfURL:pagesUrl];
PagesAccumulator *pageLoader = [[PagesAccumulator alloc] init];
pagesXmlParser.delegate = pageLoader;
[pagesXmlParser parse];
// parsing pages done
// get the pages array
self.arrayOfPages = pageLoader.arrayOfPages;
[pageLoader release];
[pagesXmlParser release];
[pagesUrl release];
NSLog(#"pagesurl retain count is:%d",[pagesUrl retainCount]);
NSLog(#"pagesxmlparser retain count is:%d",[pagesXmlParser retainCount]);
}
Thanks in advance for any assistance.
Ignore the retain counts
Just because an object has a retain count > 0 doesn't mean that it's not also autoreleased :)
Your code looks fine to me.
If it's really a leak I would look at your implementation of PageLoader to see if there is a retain in one of the NSXMLParserDelegate methods that's preventing the parser being released (which would cause the URL to leak as well).
Related
I realize this question may sound dumb, but just bear with me. I built an app to help new developers wrap their head around memory retention on the iPhone (no ARC yet). It is plain and simple, 4 buttons, init, access, retain, and release. Pretty self explanatory. I am displaying what the retain count for my string object that is the target of our poking and prodding. (Please no lectures on use of [myVar retainCount], I already know)
This stuff will never make it into actual apps, just toying with it for fun and hopefully help someone learn how memory works. My retain and release all work great. My question is that why does my retain count drop back to 1 if I call myString = [[NSMutableString alloc] init]; again. I can boost my retain count to 40, but after calling alloc/init I go back to zero. I am not leaking anywhere, just curious what happens to myString if/when alloc/init is called on it again.
My question is that why does my retain count drop back to 1 if I call
myString = [[NSMutableString alloc] init]; again?
Because you are failing to understand a very basic concept of Objective-C; myString is not an instance of an NSMutableString, but a reference to an instance. If you were to:
myString = [[NSMutableString alloc] init];
myString = [[NSMutableString alloc] init];
You now have two instances of NSMutableString, one leaked.
If you:
myString = [[NSMutableString alloc] init];
otherString = myString;
You now have a single instance of NSMutableString with two references.
In all three allocations, the NSMutableString instance will have a +1 retain count and, thus, you must balance each with a single release or you'll leak.
Treating retain counts as an absolute count is a path to madness. Or, at best, the scope of usefulness of the absolute retain count is so limited that learning about it is not applicable to real world iOS programming.
This bears repeating:
The retainCount of an object is tricky business.
If you were to continue down this path, you should be aware of the following details:
retainCount can never return 0
messaging a dangling pointer is not guaranteed to crash
retain count cannot be known once you have passed an object through any system API due to implementation details
any subclass of any system class may have an unknown retain count due to implementation details
retain count never reflects whether or not an object is autoreleased
autoreleases is effectively thread specific while the retain count is thread global
some classes are implemented with singletons some of the time (NSString, certain values of NSNumber)
the implementation details change from platform to platform and release to release
attempting to swizzle retain/release/autorelease won't work as some classes don't actually use those methods to maintain the retain count (implementation detail, changes per platform/release, etc..)
If you are going to teach retain/release, you should be treating the retain count as a delta and focus entirely on "If you increase the RC, you must decrease it".
when you call myString = [[NSMutableString alloc] init];, you're not "calling alloc/init on it again". You're not calling a method on the same instance you had. You're allocating and initializing a new instance, a completely different object from the one you had before.
And if you're doing that with a variable that had an object that you retained, then yes, you are leaking it.
Try this.
NSString *myString = [[NSMutableString alloc] init];
NSLog(#"%d", [myString retainCount]); // "1"
for (int i = 1; i < 40; i++)
[myString retain];
NSLog(#"%d", [myString retainCount]); // "40"
NSString *backup = myString;
myString = [[NSMutableString alloc] init];
NSLog(#"%d", [myString retainCount]); // "1"
NSLog(#"%d", [backup retainCount]); // "40"
You see, you have a different object with a new retain count. Your original object still exists and still has the same retain count. Assignment changes the object a variable refers to. A variable doesn't have a retain count, an object does.
myString = someOtherString;
NSLog(#"%d", [myString retainCount]); // who knows?
With retained property:
self.iString = backup;
NSLog(#"%d", [self.iString retainCount]); // "41" - 1 more because property retained
NSString *newString = [[NSMutableString alloc] init];
NSLog(#"%d", [newString retainCount]); // "1"
self.iString = newString;
// 1 for alloc 1 for retain (in real code you should release newString next)
NSLog(#"%d", [self.iString retainCount]); // "2"
NSLog(#"%d", [backup retainCount]); // "40" - self.iString released it
I have a couple of arrays that I am trying to clear all objects from, but using removeAllObjects crashes the app and returns sigabrt. During my research I've found that although I am creating NSMutableArrays I could be creating an instance of a NSArray, but I am not sure if I am doing this or not... Here is everything I do to the arrays
ballArray = [[NSMutableArray alloc] init];
ballVelocityArray = [[NSMutableArray alloc] init];
[ballArray addObject:MyUIImageView];
[ballVelocityArray addObject:[NSValue valueWithCGPoint:myCGPoint]];
[ballVelocityArray replaceObjectAtIndex:SomeIndex withObject:[NSValue valueWithCGPoint:NewVelocity]];
[ballArray removeAllObjects];
[ballVelocityArray removeAllObjects];
That is everything I have done and I can't figure out why it keeps crashing... if there is only one object in the arrays it works fine, otherwise it crashes
Any help would be greatly appreciated!!
It's most likely because you are not managing memory correctly on one of the objects the array contains. When you remove an object from an array its retain count is decremented once.
You can put a break point on the line where you clear the array and use the debugger to see which object in there is invalid.
ballArray = [[NSMutableArray alloc] init];
ballVelocityArray = [[NSMutableArray alloc] init];
After allocating object you are also releasing the object in dealloc function or somewhere else check this.If you are doing so then I would like to inform you that
[ballArray removeAllObjects];
[ballVelocityArray removeAllObjects];
removeAllObjects is not only removing all objects of array but also release the array object from memory so if again you are releasing the array object the memory pointer will reach on -1 and the application will crash.
So, make sure that You have not to release array object it you are already using
[ballArray removeAllObjects];
[ballVelocityArray removeAllObjects];
functions.
I'm working on a bible iPhone app. Here are the basics of what I'm doing so far:
My XMLParser parses an xml file and creates a Bible object
Specifically, the xml is stored in each Chapter object.
Once parsing is done, the viewController grabs a Chapter from the Bible and displays its innerHtml in a UIWebview.
This works, but whenever I try to access the Bible object outside of -(void)viewDidLoad; it either gives me a BAD_ACCESS error, or the results for what I'm asking for is unreadable. I think this is a memory management problem..
Here's what I'm doing in the viewController
- (void)viewDidLoad
{
[super viewDidLoad];
//Create parser and XML data object.
//Then, parse that data
finalBible = [[Bible alloc]init];
NSString *filePath = [[NSBundle mainBundle] pathForResource:#"KJV" ofType:#"html"];
NSData *myData = [NSData dataWithContentsOfFile:filePath];
//INT I WANTED TO USE TO ITERATE WHEN BUTTON WAS PRESSED TO ADVANCE TO NXT CHAPTER
chapToShow = 2;
parser = [[XMLParser alloc] init];
nsParser = [[NSXMLParser alloc] initWithData:myData];
//set delegate for NSXMLParser
[nsParser setDelegate:parser];
//PARSE THE XML FILE AND BUILD BIBLE OBJECT - PARSED OK!!
if ([nsParser parse]) {
NSLog(#"Parsed with no errors!! :)");
}else{
NSLog(#"Error parsing document");
}
//IT SEEMS MY PROBLEMS MAY BE IN THIS TRADE OFF.
//I WANT TO STORE THE PARSER'S BIBLE IN THIS NEW BIBLE OBJECT.
finalBible = [parser getBible];
//Test querying bible via pullVerse method - IT WORKS!!
NSLog(#"%#",[finalBible pullVerse:#"65.021.000"]);
NSString *firstChap = [[[[finalBible getTestament:0]getBook:#"Genesis"]getChapterWithInt:3]getInnerHtml];
//Try and load Genesis 1 - THIS WORKS!!
NSLog(#"...Loading Genesis 1...");
[bibleView loadHTMLString:firstChap baseURL:nil];
//LOADING THE VERSION WORKS HERE!!
NSLog(#"Version = %#", [finalBible getVersion]);
}
- (IBAction)buttonPressed:(id)sender {
NSLog(#"Now reading chapter %d", chapToShow);
//HERE I'M TRYING TO GET THE BIBLE VERSION BUT THE APP CRASHES AS A RESULT
NSLog(#"Testing the bible: Version = %# \n OK", [finalBible getVersion]);
//NOTE: I've even tried [[parser getBible] getVersion] and it still doesn't work.
// I don't release the parser till the view's dealloc method, so I'm not sure why I
// can't access it here...
}
Of course, I'd be happy to post any other code. I just didn't want to over-stuff the page with code, so I pasted only where I think the problem lies, or at least where it's occurring.
You allocate finalBible, but then you set finalBible = [parser getBible] so the previous allocation is pointless. Also, it appears as though [parser getBible] returns an autoreleased object, so you should call [[parser getBible] retain] to make sure it does not leave memory.
This is exactly what you need to do in your .h file add this line:
#property(nonatomic, retain) Bible finalBible;
Then in your .m file add this line at the top:
//This generates the methods (get, set) for your instance variable
#synthesize finalBible;
Then drop this line:
finalBible = [[Bible] alloc]init];
This is because if you keep it, there will be a memory leak right here:
finalBible = [parser getBible];
Because now you are pointing to a new memory location, and the previous memory location had an object with a retain count of 1 provided by alloc init, and since there will no longer be any reference to this object it will never be released causing a memory leak.
Although if you use this line:
self.finalBible = [parser getBible];
Because that uses the setter, a setter releases the previous value and retains the new one, so there would not be a memory leak, but it would still be pointless to allocate that object.
Since getBible does not have the new, alloc or init keyword it should return an autoreleased object, which is why the object is released in the next run loop (not guaranteed but most likely), which is why you cannot access it outside of the viewDidload() method.
You can resolve this problem by making "finalBible" variable a property of the class using
#property(nonatomic, retain) Bible finalBible; //this is in the .h file
#synthesis finalBible; // at the top of .m file
All the reference to "finalBible" should be made as "self.finalBible"
It is normal to have such issues but I am currently stuck in knowing how it works.
Whenever I use NSXMLparser to parse the URL and store in the database, it gets parsed for the first time but when I parse it again it throws EXC_BAD_ACCESS.
Here is my code:
- (void) initParse {
[super init];
appleAppDelegate = (appleAppDelegate*)[[UIApplication sharedApplication] delegate];
NSURL *url = [[[NSURL alloc] initWithString:#"http:example.com/file.xml"] autorelease];
self.parser1 = [[[NSXMLParser alloc] initWithContentsOfURL:url] autorelease] ;
[parser1 setShouldResolveExternalEntities:NO];
[parser1 setDelegate:self];
[parser1 parse];
}
When it reaches the end of the function at "}", it throws EXC_BAD_ACCESS. I am not sure what is wrong since I am releasing my URL and even my parser.
Has any one come across this situation.
Sagos
Try running with NSZombieEnabled - that will tell you the type of the object which is being accessed after being freed.
You are accessing a released object which is exactly your problem, make sure you release at the end and make sure everything you need is still around.
I am developing an iphone app. Instruments reported a leaked object ServiceTypes. Below is the relevant code. Does anyone have any ideas? Thanks a lot for your help.
ServiceTypes *serviceTypes = [[ServiceTypes alloc] init];
if ([userConnection getServiceTypes:serviceTypes]) {
if ([serviceTypes.types length] > 0) {
NSArray *array = [[NSArray alloc] initWithArray:[serviceTypes.types componentsSeparatedByString: SERVICE_TYPE_DELIMITOR]];
serviceRequestTypes = [[NSMutableArray alloc] initWithArray:array];
[array release];
}
}
[[self typesTableView] reloadData];
[serviceTypes release];
It doesn't look like serviceTypes is being leaked. From the code you posted, serviceTypes is always released at the end of the method, and it doesn't appear to be retained anywhere in your sample. My question is: what happens inside getServiceTypes:. Does that method retain the serviceTypes parameter?
One more thing. If serviceRequestTypes is an instance variable (and it looks like it is), then you may be leaking memory by reassigning it without releasing the existing serviceRequestTypes object first. You should either rewrite serviceRequestTypes to be a property and use a synthesized accessor or make sure to release it every time before assigning. If its current value is nil, no big deal; the release message will simply be ignored. For example:
[serviceRequestTypes release];
serviceRequestTypes = [[NSMutableArray alloc] initWithArray:[serviceTypes.types componentsSeparatedByString:SERVICE_TYPE_DELIMITER]];