So in my view controller, I run code to populate an NSArray of Customer (custom class) objects. This custom class has objects that are of ANOTHER custom class called Address (a customer has a billing address and a shipping address). In the view controller when a customer in the list is selected, it passes a new view controller a customer object, like so:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
InfoViewController *customerinfoViewController = [[InfoViewController alloc] initWithStyle:UITableViewStyleGrouped andCustomer:[[[customers objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] retain]];
[self.navigationController pushViewController:customerinfoViewController animated:YES];
[customerinfoViewController release];
}
The first time I visit this view controller while running the application, it works fine. However, when I revisit the view controller, something interesting happens. The application crashes, with unrecognized selector sent to instance 0x00whatever. Using the mouseover debugging feature in xCode, I am finding that the first object of the customer's shipAddress variable has its type changed from NSString to NSIndexPath. This does not happen to the customer's billAddress object. Anyone have any idea what is going on here? It seems like I may be having memory management issues but I would definitely like a confirmation on this before I tear my code apart tracking down all the retains and releases....
EDIT: More information here. with the following code, I have an NSMutableArray at the class level. At each iteration of the loop, I am looping through nodes in XML (which works fine). Every time a new letter is detected as the first letter of the name, I create a new subarray and add the customer to it, thus filling my class-level NSMutableArray (customers) with subArrays of customers for each letter of the alphabet detected. My question is about the retains and releases of the cycling customer object. Clang Static says there is an over-retaining error on the customer, but when I fix it according to Clang, the loop crashes. what gives? Related code below:
DDXMLDocument *rootDoc = [[[DDXMLDocument alloc] initWithData:xmlData options:0 error:nil] autorelease];
NSArray *elems = [rootDoc nodesForXPath:#"QBXML/QBXMLMsgsRs/CustomerQueryRs/CustomerRet" error:nil];
DDXMLNode *node;
sectionTitles = [[[NSMutableArray alloc] initWithCapacity:1] retain]; // Letters for UITableView section titles
NSMutableArray *subArray;
NSString *lastchar = #"A";
NSString *testchar;
int indexCount = -1;
customers = [[[NSMutableArray alloc] initWithCapacity:[elems count]] retain];
Customer *newCust;
for (int i = 0; i < [elems count]; i++) {
node = [elems objectAtIndex:i];
newCust = [[Customer alloc] initWithCustomerRetNode:node];
testchar = [[newCust fullName] substringToIndex:1];
if (i == 0 || ![[testchar uppercaseString] isEqualToString:lastchar]) {
[sectionTitles addObject:testchar];
lastchar = testchar;
indexCount++;
subArray = [[NSMutableArray alloc] initWithCapacity:1];
[customers addObject:subArray];
[subArray release];
[[customers lastObject] addObject:[newCust retain]];
}
else {
[[customers lastObject] addObject:[newCust retain]];
}
[newCust release];
}
NOTE: this code works for the most part, but clang doesn't like it.
EDIT: Addresses in the Customer class are assigned like so (which now does not work after Clang fixes)
...
else if ([tempname isEqualToString:#"BillAddress"])
billAddress = [billAddress initWithAddressNode:tempnode];
else if ([tempname isEqualToString:#"ShipAddress"])
shipAddress = [shipAddress initWithAddressNode:tempnode];
...
It sounds like you are having a over release issue, so yes memory management, you might be overreleasing that array you are storing your objects in.Cant really tell from the snippet of code though. Youll have to go and look through the code and find the source. Also using Clang Static Analyzer might be of help to you.
Related
I am developing an iphone application which has some data stored in a sqllite database. When my view loads i would like to load the data from the database on a background thread. The problem is the application keeps crashing and i dont know why.
The code:
-(id) init
{
if((self=[super init]))
{
[self performSelectorInBackground:#selector(loadList) withObject:nil];
}
}
-(void) loadList
{
#autoreleasepool
{
Loader * loader = [[Loader alloc] init];
NSMutableArray * array = [loader getItemList];
[array retain];
NSLog(#"Got %d items",[array count]);
[self performSelectorOnMainThread:#selector(createList:) withObject:array waitUntilDone:false];
[loader release];
}
}
-(void) createList: (NSMutableArray*) array
{
items = array;
int i;
Item * it;
for(i = 0; i < [items count]; i++)
{
it = [items objectAtIndex: i];
[it getName]; // crashes
// populate the list
}
}
Loader returns a NSMutableArray with Item objects. The application crashes when i call the item getName (which returns a NSString*). From what i understand it crashes because the item name properties is being released. What am i doing wrong?
Thanks!
It's likely to be a problem with whatever type of object you're using to populate array.
I'm unable to find finger-on-paper proof but I'm confident that performSelectorOnMainThread:withObject:waitUntilDone: retains its object. However if each of the items in array keeps a reference to loader then they need to take responsibility for retaining that object. It looks like you're attempting to keep it alive manually but — as Chuck alludes to — your call to performSelector... will return instantly and not wait for the call you've made to complete.
This particular bug appears to be that you're passing waitUntilDone:NO, so the array is being released immediately and consequently so are its items.
But in general, UIKit is not thread-safe, so this is just a touchy design. I would probably put the loading of this stuff in another class that handles the task for you instead of right in the view.
I'd put a breakpoint on the line:
it = [items objectAtIndex: i];
Then type
po it
in the debugger, and see what's in the name field. As a guess, I'd say one of two things: 1) the field that getName returns isn't initialized with an object (i.e. isn't a real NSString *) or that you're getting a C string from SQLite (which is what it usually returns) and you're trying to treat it as an NSString *. If it's the latter you can use [myCString stringWithUTF8String] to convert the C string into an NSString *
Instruments is saying there is a memory leak in this code:
- (void)layoutImageMaskViewForImageAtPath:(NSString *)path withFillColor:(UIColor *)color indexPath:(NSIndexPath *)indexPath {
UIImage *image = [UIImage imageWithContentsOfFile:path];
[self layoutImageMaskViewForImage:image withFillColor:color indexPath:indexPath];
}
UIColor *anIconFillColor = [UIColor colorWithWhite:0.70 alpha:1.0];
NSIndexPath *anIndexPath = [NSIndexPath indexPathForRow:0 inSection:0];
NSString *aPlaceholderPath = [[NSBundle mainBundle] pathForResource:#"path" ofType:#"png"];
[self layoutImageMaskViewForImage:anImage withFillColor:anIconFillColor indexPath:anIndexPath];
and
NSDictionary *anAssignedData = [aReservationData objectForKey:kAssignedSectionKey];
NSMutableArray *anEmployeeTaskQueueList = [NSMutableArray array];
NSArray *anAssignedReservationData = [anAssignedData objectForKey:kEmployeesIdentifier];
for (NSDictionary *aJobQueueData in anAssignedReservationData) {
EmployeeReservationQueue *anAssignedTaskQueue = [[EmployeeReservationQueue alloc] initWithServerDictionary:aJobQueueData];
if (anAssignedTaskQueue.rows.count == 0) {
ReservationTrack *aTrack = [[ReservationTrack alloc] init];
aTrack.rowSortOrder = 0;
aTrack.reservations = [NSArray array];
anAssignedTaskQueue.rows = [NSArray arrayWithObject:aTrack];
[aTrack release];
}
[anEmployeeTaskQueueList addObject:anAssignedTaskQueue];
[anAssignedTaskQueue release];
}
Your second example leaks track. Your last line is releasing aTrack instead.
In second case here:
[aTrack release];
What is aTrack? May be you mean [track release];?
In first case probably that you pass to function non-autoreleased parameters or may be you are not releasing them after calling that method. Just post code where you call for that method and I will check.
Gold memory-management rule in Objective-C :
Each 'init', 'copy','mutableCopy','retain' must call then 'release' or 'autorelease'.
Instruments reports that your app is leaking a ReservationTrack object. By default it shows where the leaked object was allocated, which is the code you posted. The code you posted doesn't leak a ReservationTrack. It stores it in an EmployeeReservationQueue which is stored in an NSMutableArray. One possibility is that you later access the ReservationTrack object, send it retain, and don't send it release or autorelease. Another possibility is that you leak the EmployeeReservationQueue or the NSMutableArray.
If you use the simulator, you can see the full retain/release history of most objects. When a leaked object shows up, mouse over the address of the object and click the right arrow that appears next to the address. Instruments will show you every malloc, retain, release, and autorelease event for that object. If you choose View > Extended Detail from the menu bar, you can click on any of those events and see the stack trace of the event. This should help you track down the unbalanced retain.
I'm new to cocoa / objective-c and i'm struggeling with the releases of my objects. I have the following code:
gastroCategoryList = [[NSMutableArray alloc] init];
for (NSDictionary *gastrocategory in gastrocategories) {
NSString *oid = [gastrocategory objectForKey:#"id"];
GastroCategory *gc = [[GastroCategory alloc] initWithId:[oid intValue] name:[gastrocategory objectForKey:#"name"]];
[gastroCategoryList addObject:gc];
}
The analyzer shows me that the "gastrocategory" defined in the for is a potential memory leak. But i'm not sure if i can release this at the end of the for loop?
Also at the following code:
- (NSArray *)eventsForStage:(int)stageId {
NSMutableArray *result = [[NSMutableArray alloc] init];
for (Event *e in eventList) {
if ([e stageId] == stageId) {
[result addObject:e];
}
}
return result;
}
The Analyzer tells me that my "result" is a potential leak. But where should I release this?
Is there also a simple rule to memorize when i should use assign, copy, retain etc. at the #property ?
Another problem:
- (IBAction)showHungryView:(id)sender {
GastroCategoriesView *gastroCategoriesView = [[GastroCategoriesView alloc] initWithNibName:#"GastroCategoriesView" bundle:nil];
[gastroCategoriesView setDataManager:dataManager];
UIView *currentView = [self view];
UIView *window = [currentView superview];
UIView *gastroView = [gastroCategoriesView view];
[window addSubview:gastroView];
CGRect pageFrame = currentView.frame;
CGFloat pageWidth = pageFrame.size.width;
gastroView.frame = CGRectOffset(pageFrame,pageWidth,0);
[UIView beginAnimations:nil context:NULL];
currentView.frame = CGRectOffset(pageFrame,-pageWidth,0);
gastroView.frame = pageFrame;
[UIView commitAnimations];
//[gastroCategoriesView release];
}
I don't get it, the "gastroCategoriesView" is a potential leak. I tried to release it at the end or with autorelease but neither works fine. Everytime I call the method my app is terminating. Thank you very much again!
In your loop, release each gc after adding it to the list since you won't need it in your loop scope anymore:
gastroCategoryList = [[NSMutableArray alloc] init];
for (NSDictionary *gastrocategory in gastrocategories) {
NSString *oid = [gastrocategory objectForKey:#"id"];
GastroCategory *gc = [[GastroCategory alloc] initWithId:[oid intValue] name:[gastrocategory objectForKey:#"name"]];
[gastroCategoryList addObject:gc];
[gc release];
}
In your method, declare result to be autoreleased to absolve ownership of it from your method:
NSMutableArray *result = [[[NSMutableArray alloc] init] autorelease];
// An alternative to the above, produces an empty autoreleased array
NSMutableArray *result = [NSMutableArray array];
EDIT: in your third issue, you can't release your view controller because its view is being used by the window. Setting it to autorelease also causes the same fate, only delayed.
You'll have to retain your GastroCategoriesView controller somewhere, e.g. in an instance variable of your app delegate.
BoltClock's answer is spot-on as to the first part of your question. I'll try to tackle the rest.
Assign is for simple, non-object types such as int, double, or struct. It generates a setter that does a plain old assignment, as in "foo = newFoo". Copy & retain will, as their names imply, either make a copy of the new value ("foo = [newFoo copy]") or retain it ("foo = [newFoo retain]"). In both cases, the setter will release the old value as appropriate.
So the question is, when to copy and when to retain. The answer is... it depends. How does your class use the new value? Will your class break if some other code modifies the incoming object? Say, for example, you have an NSString* property imaginatively named "theString." Other code can assign an NSMutableString instance to theString - that's legal, because it's an NSString subclass. But that other code might also keep its own reference to the mutable string object, and change its value - is your code prepared to deal with that possibility? If not, it should make its own copy, which the other code can't change.
On the other hand, if your own code makes no assumptions about whether theString might have been changed, and works just as well whether or not it was, then you'd save memory by retaining the incoming object instead of unnecessarily making a copy of it.
Basically, the rule, which is unfortunately not so simple sometimes, is to think carefully about whether your own code needs its own private copy, or can correctly deal with a shared object whose value might be changed by other code.
The reason you can release gc after it is added to the gastroCategoryList is that when an object is added to an array, the array retains that object. So, even though you release your gc, it will still be around; retained by the gastroCategoryList.
When you are returning a newly created object from a method, you need to call autorelease. This will cause the object to be released only after the runtime leaves the scope of the calling method, thereby giving the calling method a chance to do something with the returned value.
Note that if your method starts with the word copy or new, then you should not autorelease your object; you should leave it for the calling method to release.
As for copy vs retain vs assign... as a general rule, copy objects that have a mutable version, such as NSArray, NSSet, NSDictionary, and NSString. This will ensure that the object you have a pointer to is not mutable when you don't want it to be.
Otherwise, use retain whenever you want your class to be ensured that an object is still in memory. This will apply to almost every object except for objects that are considered parents of your object, in which case you would use assign. (See the section on retain cycles here).
Also note that you have to use assign for non-object types such as int.
Read through the Memory Management Programming Guide a bit; it's quite helpful.
I have 4 UITextFields that I'm dynamically creating, in the viewDidLoad, which works good. I want to reference those objects when the UISlider value changes. Right now I'm storing those objects in a NSMutableArray and accessing them like so from the sliderChanged method:
NSInteger labelIndex = [newText intValue];
labelIndex--;
NSUInteger firstValue = (int)0;
NSMutableArray *holeArray = [pointsArray objectAtIndex:labelIndex];
UITextField *textField = [textFieldArray objectAtIndex:firstValue];
NSString *newLabel1Text = [[NSString alloc] initWithString:[[holeArray objectAtIndex:firstValue] stringValue]];
[textField setText: newLabel1Text];
[newLabel1Text release];
Everything is working good, but the program crashes on the setText: method. The last message I get from the program is: [UILabel drawTextInRect:] and then I get a EXC_BAD_ACCESS failure.
I want to be able to acces that dynamically created UITextField, but I must be going about it the wrong way.
Thanks!
Uh, yea, you create a text field, but you aren't displaying the field itself, just creating it.
If you want to do what I think you want to do, I would just do if statements.
ex.
if (firstValue == 1)
{
fieldone.text = #"whatever";
}
else if (firstValue == 2)
{
fieldtwo.text = #"whatever";
}
I have a table view in which I'm using sectionIndexTitlesForTableView to display an index. However, when I scroll the table, the index scrolls with it. This also results in very slow refreshing of the table. Is there something obvious I could be doing wrong? I want the index to remain in place on the right while the table scrolls. This is the code I'm using for the index titles:
- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView {
NSMutableArray *tempArray = [[NSMutableArray alloc] init];
[tempArray addObject:#"A"];
[tempArray addObject:#"B"];
[tempArray addObject:#"C"];
[tempArray addObject:#"D"];
...
return tempArray;
}
You really should be creating the index list somewhere else (say, in your table controller's init or loadView methods) and retaining it as an instance variable for later use. Then in sectionIndexTitlesForTableView you only have to return that ivar. If it isn't a property with a retain attribute then make sure you retain it when created so it sticks around (and release it in dealloc).
An easy way to create it is:
self.alphabetIndex = [NSArray arrayWithArray:
[#"A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z|#"
componentsSeparatedByString:#"|"]];
The actual letters would have to change depending on the language locale setting but this way it's a bit easier to localize.
You definitely don't want to be creating that temp array each time because it's going to get called a lot.
As far as the index scrolling away it may be related to your returning a new array each time. Try the above first and if it doesn't solve the problem then you may want to tweak the value for the table's sectionIndexMinimumDisplayRowCount property and see if it makes any difference.
I would avoid creating a new NSMutableArray and releasing it every time. Try creating those on viewDidLoad or the class constructor and just reference the pre-built array on sectionIndexTitesForTableView.
If you are not manipulating the array at all, you probably don't need the overhead of an NSMutableArray at all. Try switching it to a plain old NSArray by using the arrayWithObjects static autorelease constructor.
That should speed things up for you.
Make a static variable, it will be released on app exit.
static NSMutableArray* alphabet = nil;
+ (void)initialize {
if(self == [MyViewController class]){
NSUInteger const length = 'Z' - 'A' + 1;
alphabet = [[NSMutableArray alloc] initWithCapacity:length];
for(NSUInteger i=0; i<length; ++i){
unichar chr = 'A' + i;
[alphabet addObject:[NSString stringWithCharacters:&chr length:1]];
}
}
}