I have a UIViewController. At the top of the UIViewController, I have declared
NSMutableArray *contacts;
In my viewDidLoad method, I call [self getContacts] which basically initializes my contacts array. It begins by initializing the array, and then it adds some objects:
if(contacts == nil)
contacts = [[NSMutableArray alloc] init];
[contacts removeAllObjects];
[contacts addObjectsFromArray:[some objects]];
So, now my contacts is initialized. In my viewDidLoad method, I even use contacts, and it works great. Later on, in a method, I need to retrieve the elements of contacts, however I am getting an EXC_BAD_ACCESS. Why is this? Why doesn't my contacts array keep the objects that I initialized it with in the beginning, and how do I fix this?
EDIT:
The error comes when I select a NavigationBarItem which then triggers a method buttonWasPressed. In that method, I simply have the following:
-(void)buttonWasPressed:(id)sender {
NSLog(#"button was pressed");
if(contacts == nil)
NSLog(#"contacts is nil!");
NSLog(#"contacts = %#",contacts);
}
And I see "button was pressed" printed, but then there is an EXEC_BAD_ACCESS.
That code all looks good, nothing wrong there. I would guess you are over-releasing elsewhere. Turn on Zombies - add NSZombieEnabled to YES in the executable arguments and it will break on the line so you can see what object is being over-released.
Related
i have an UITableView and im trying to return the number of rows using [arrayName count] however when i run the application it seems to be crashing with no errors showing in console. Here is some code .. (also when i test the array in ViewDidLoad using NSLog, it does return '16' so im not sure why it crashes when i do the row count. Thanks ..
I think the problem is in this line:
elements = [xpathParser search:#"//div[starts-with(#id,'content_div')]//a"];
I guess the - search method returns an autoreleased object, so that your elements object receives the release message after the method viewDidLoad returns and hence gets deallocated.
You can fix this in two ways:
add a retain call, like this
elements = [[xpathParser search:#"//div[starts-with(#id,'content_div')]//a"] retain];
use properties, like this
self.elements = [xpathParser search:#"//div[starts-with(#id,'content_div')]//a"];
You don't need to release htmldata as it is already autoreleased. Remove the [htmldata release]; line and it should work.
Also, you don't, ever, release an object after the [super dealloc] line. Bring the line [elements release]; before the super dealloc.
You don't do a retain on elements, and when you assign it, you assign it directly to the property, and don't go through the setter.
Try:
self.elements = [xpathParser search:#"//div[starts-with(#id,'content_div')]//a"];
Also, don't forget to release it in the dealloc method.
General noob questions:
(1) How can I create an NSMutable array in a buttonClicked action that I can add more entries to during subsequent clicks of the same button? I always seem to start over with a new array at every click (the array prints with only 1 entry which is the most recent button's tag in an NSLog statement).
I have about 100 buttons (one for each character in my string called "list") generated by a for-loop earlier in my code, and each has been assigned a tag. They are in a scrollview within the view of my ViewController.
I wish to keep track of how many (and which ones) of the buttons have been clicked with the option of removing those entries if they are clicked a second time.
This is what I have so far:
-(void) buttonClicked:(UIButton *)sender
NSMutableArray * theseButtonsHaveBeenClicked = [[NSMutableArray alloc] initWithCapacity: list.length];
NSNumber *sendNum = [NSNumber numberWithInt:sender.tag];
[theseButtonsHaveBeenClicked addObject:sendNum at index:sender.tag];
NSLog(#"%#",theseButtonsHaveBeenClicked);
}
(2) I have read that I may be able to use a plist dictionary but I don't really understand how I would accomplish that in code since I cant type out the items in the dictionary manually (since I don't know which buttons the user will click). Would this be easier if I somehow loaded and replaced the dictionary in a plist file? And how would I do that?
(3) I also have no idea how I should memory manage this since I need to keep updating the array. autorelease?
Thanks for any help you can provide!
Okay, firstly you are creating a locally scoped array that is being re-initialised on every call to buttonClicked:. The variable should be part of the class init cycle.
You will also be better off with an NSMutableDictionary instead of an NSMutableArray. With a dictionary we don't have to specify capacity and we can use the button's tags as dictionary keys.
Here's what you need to do, these three steps always go together: property/synthesize/release. A good one to remember.
//Add property declaration to .h file
#property (nonatomic, retain) NSMutableDictionary * theseButtonsHaveBeenClicked;
//Add the synthesize directive to the top of .m file
#synthesize theseButtonsHaveBeenClicked;
// Add release call to the dealloc method at the bottom of .m file
- (void) dealloc {
self.theseButtonsHaveBeenClicked = nil; // syntactically equiv to [theseButtonsHaveBeenClicked release] but also nulls the pointer
[super dealloc];
}
Next we create a storage object when the class instance is initialised. Add this to your class's init or viewDidLoad method.
self.theseButtonsHaveBeenClicked = [[NSMutableDictionary alloc] dictionary]; // convenience method for creating a dictionary
And your updated buttonClicked: method should look more like this.
-(void) buttonClicked:(UIButton *)sender {
NSNumber *senderTagAsNum = [NSNumber numberWithInt:sender.tag];
NSString *senderTagAsString = [[NSString alloc] initWithFormat:#"%#",senderTagAsNum];
// this block adds to dict on first click, removes if already in dict
if(![self.theseButtonsHaveBeenClicked objectForKey:senderTagAsString]) {
[self.theseButtonsHaveBeenClicked setValue:senderTagAsNum forKey:senderTagAsString];
} else {
[self.theseButtonsHaveBeenClicked removeObjectForKey:senderTagAsString]; }
[senderTagAsString release];
NSLog(#"%#", self.theseButtonsHaveBeenClicked);
}
Serious Problem here... i'm getting ECX_BAD_ACCESS if i try to NSLog an instance variable of my custom object. Following Function is called in my ViewController, payload holds String Data which is pulled from a url.
- (void) initVcardWithData:(NSString *)payload {
NSLog(#"1. initVcardWithData");
aVCard = [[vcardItem alloc] initWithPayload:payload];
VCardViewController *aVCardViewController = [[VCardViewController alloc] initWithVCard:aVCard];
[self presentModalViewController:aVCardViewController animated:YES];
[aVCard release];
}
So far so good. The initWithWithVCard function is as follows, theVCard and theVCardN are defined in #implementation and also set as a #property (nonatomic, retain) in (.h).:
-(id)initWithVCard:(vcardItem *)aVCard {
if(self = [super init]) {
theVCard = [aVCard retain];
theVCardN = [theVCard.PersonName retain];
}
NSLog(#"---- vCardViewController :: initWithVcard :: FirstName: %#", theVCard.PersonName.FirstName);
return self;
}
If i access the theVCardN object in my ViewController aVCardViewController within ViewDidLoad everything works like a charm. I set some labels with data from that object.
If i then try to access the instance variables from theVCardN within a function which is called from an IBAction which is connected to a button in View, i get an EXC_BAD_ACCESS error at the debugger console. The Function which tries to pull data from the instance variables is as follows:
-(IBAction)addressbookButtonTapped {
NSLog(#"RETAIN COUNT FOR theVCard: %i", [theVCard retainCount]);
NSLog(#"RETAIN COUNT FOR theVCardN: %i", [theVCardN retainCount]);
NSLog(#"Save to Adressbook: %#", theVCardN.FirstName);
//[self dismissModalViewControllerAnimated:YES];
}
The RetainCounter for theVCardN right before calling NSLog outputs "1". The NSLog Line then returns EXC_BAD_ACCESS in Debugger Console.
Any idea ?
Do not call -retainCount. Absolute retain counts are useless.
retainCount returns the absolute retain count of an object. The actual value will be an implementation detail that is very often completely out of your control as the system frameworks may do any number of things internally to cause the retain count to be modified in ways you don't expect.
It is useless for debugging and their are a wealth of tools that are specifically focused on tracking down these kinds of issues.
First, if there is a crash, there is a backtrace. Post it. Probably not that interesting in this case, but, still, always look to the backtrace to at least confirm that it is crashing where/how you think it is.
From the evidence posted, it sounds like theVCardN.FirstName is either set to garbage or the underlying string has been over-released. Turn on zombie detection mode and see if that is the case. Since it is crashing on FirstName, then show the code related to creating/storing the FirstName.
Also, instance variables and methods should always start with a lowercase letter; PersonName should be personName & FirstName should be firstName.
Maybe i'm reading the code wrong or misunderstanding your class structure, but it looks like you logging:
NSLog(#"Save to Adressbook: %#", theVCardN.FirstName);
Above, where you say it is still working, you are logging:
theVCard.PersonName.FirstName
Are you missing the "PersonName"? Meaning you should be logging:
NSLog(#"Save to Adressbook: %#", theVCardN.PersonName.FirstName);
i have this array called favorites referenced in my app delegate.
When i access it in the view controller i use this code
MultiViewAppDelegate *app = (MultiViewAppDelegate *)[[UIApplication sharedApplication] delegate];
[app.favoritesArray addObject:#"one"];
And in the table thats supposed to display this information im trying to ask if the array contains a certain element and if it does to display that item using this code.
NSLog (#"2");
favoritesArray = [[NSMutableArray alloc]init];
didContain = [[NSMutableArray alloc]init];
NSLog (#"3");
if ([favoritesArray containsObject:#"one"])
{[didContain addObject:#"one"];
NSLog (#"4"); }
however the code isnt running after nslog 3...
can someone inform me why?
Firstly,
NSLog (#"2");
favoritesArray = [[NSMutableArray alloc]init];
The above line will reset your favoritesArray. It will also leak the old one.
didContain = [[NSMutableArray alloc]init];
NSLog (#"3");
if ([favoritesArray containsObject:#"one"])
Here, you're simply asking an empty array if it contains something, which it obviously doesn't.
{[didContain addObject:#"one"];
NSLog (#"4"); }
Which is why none of the above ever happens.
Instead of resetting it, make sure it's set instead.
if (favoritesArray != nil &&
[favoritesArray containsObject:#"one"]) {
NSLog(#"yay, it had one in it");
} else {
NSLog(#"it's nil or it didn't have one in it");
}
You probably don't need favoritesArray != nil, but I put it in because you might have put your alloc-init stuff in because you sometimes get a nil value here. Unlikely though.
if ([favoritesArray containsObject:#"one"]) {
// contains "one"
}
That should probably do it.
Check if favoritesArray in your delegate is initialized. If it is nil, the condition will never be true.
I'm doing an iPhone application which uses a navigation control to browse through some data. This data is stored in a sqlite database and I have a class which gets it and returns it in a NSMutableArray of NSStrings.
The problem is that in the first screen of the navigation everything works prefectly, but in the second screen (another view which is pushed) the same code fails because the NSMutableArray gets corrupted. In the debugger I can see that it is returned correctly, but when it's time to use it the pointers have become corrupted and the application crashes.
I have put breakpoints in all my functions, and I can't see anywhere where it can get corrupted. And as the first view, which uses the same exact code, even accesing the same eact tables, works correctly I don't really know where to look.
If anyone want to have a look at the code I have uploaded it to my site: http://sachafuentes.com/iBacus.zip
Thanks in advance.
UPDATE:
The problem lies in the function where I get the data, which looks like (this is a simplified version with some pseudo-code).
-(NSMutableArray *) getPaises {
NSMutableArray * paises;
paises = [[NSMutableArray alloc] init];
while( get new row ) {
NSString *aPais = get the value;
[paises addObject:aPais];
[aPais release];
}
return paises;
}
If I comment out [aPais release] everything works, but to me this looks like a memory leak, as the NSString won't be released.
Okay, here's the problem:
NSString *aPais = [NSString stringWithUTF8String:(char*)sqlite3_column_text(compiledStatement, 0)];
By convention, any time that you see an alloc and an init, you need a release somewhere down the road.
By convention, any time that you use an xWithX: style method, the resulting object will be released for you.
Therefore, this statement:
[aPais release];
will cause your method to crash, as the object is released before it should be. Just remove this line, set your NSMutableArray instance to be autorelease-d and you should get better results.
Look for wrong memory management, that's the likeliest cause for crashes. I think you release your objects somewhere where you shouldn't and therefore you have dangling pointers in the array.
Update1
[aPais release] is wrong, as you don't retain it anywhere in this method. Returned values should always be autoreleased. You should have the same amount of retain as release in your code.
(Some people argue that a retain can also be an alloc init, but I always try to use alloc init autorelease, but this is a matter of style.)
BTW
You should autorelease your array, you're only retaining it here with [[alloc] init].
Any object that you alloc and init must be release-d when you're finished with it, or you will have a memory leak.
Since you are passing the reference outside the scope of the getPaises method, you must autorelease the NSMutableArray, or you will have a memory leak:
paises = [[[NSMutableArray alloc] init] autorelease];
Can you please clarify the step here:
NSString *aPais = get the value;
It's not clear what happens in "get the value" and I suspect this is one cause of instability.
I see that the code is (verbatim)
while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
NSString *aPais = [NSString stringWithUTF8String:
(char*)sqlite3_column_text(compiledStatement, 0)];
[paises addObject:aPais];
[aPais release];
}
...and it's exactly as #gs puts it. aPais is autoreleased and should not be released.
You can also use a convenience constructor to initialize the NSMutableArray:
NSMutableArray *paises = [NSMutableArray array];
This is equivalent to doing:
NSMutableArray *paises = [[[NSMutableArray alloc] init] autorelease];