dealloc

Does the order of statements in the dealloc method matter? Does the [super dealloc] need to be at the top of the method? Does it matter? Also in e.g. viewDidLoad . Should [super viewDidLoad] be at the top of the method? It ABSOLUTELY matters. What you do depends on whether you're using Automatic Reference Counting (ARC) or manual reference counting. Using Manual Release-Retain Manual Release-Retain (MRR) is default memory management for all versions of Mac OS X, and the only way to handle memory until Xcode 4.2. With MRR, [super dealloc] should be at the end of your method. So your code should

When a custom class is created in Objective C, when and how is the dealloc method called? Is it something that I have to implement somehow in my class? You never send a dealloc message directly. Instead, an object’s dealloc method is invoked indirectly through the release NSObject protocol method (if the release message results in the receiver's retain count becoming 0). See Memory Management Programming Guide for more details on the use of these methods. Subclasses must implement their own versions of dealloc to allow the release of any additional memory consumed by the object—such as

Looking at various Apple examples (for example Add Music ) in which I see they add observers to the default NSNotificationCenter in viewDidLoad , then remove them in dealloc . This seems dangerous as viewDidLoad can be called multiple times without dealloc being called. This would then add the same observer multiple times, causing the handler to be called multiple times. A solution to this would be to also remove observers in viewDidUnload , but this would then mean the same observer could be removed for a second time in dealloc which seems like a potential problem. What am I missing? Lorenzo

I am writing a framework and I have an object with a custom init method: @implementation OSDatabase @synthesize database; // MEM - (void)dealloc { sqlite3_close(database); [super dealloc]; } // INIT - (id)initWithDatabasePath:(NSString *)path error:(NSError **)error { if (self = [super init]) { if (!sqlite3_open_v2([path UTF8String], &database, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, NULL)) { error = [NSError errorWithDomain:@"OSDatabaseErrorDomain" code:1 userInfo:nil]; [self dealloc]; return nil; } } return self; } @end Is it safe to call dealloc inside of an init method if an error

In Clang's Objective-C Automatic Reference Counting we see the following For __weak objects, the lvalue is updated to point to the new pointee, unless the new pointee is an object currently undergoing deallocation, in which case the lvalue is updated to a null pointer. This must execute atomically with respect to other assignments to the object, to reads from the object, and to the final release of the new pointee. In objc-weak.mm wee see the following chunk of code in weak_register_no_lock() : if (deallocating) { if (crashIfDeallocating) { _objc_fatal("Cannot form weak reference to instance (

How can I free part of list's memory in python? Can I do it in the following manner: del list[0:j] or for single list node: del list[j] Mark: My script analyzes huge lists and creates huge output that is why I need immediate memory deallocation. You cannot really free memory manually in Python. Using del decreases the reference count of an object. Once that reference count reaches zero, the object will be freed when the garbage collector is run. So the best you can do is to run gc.collect() manually after del -ing a bunch of objects. In these cases the best advice is usually to try and change