Why we use #autoreleasepool in ios 5?
My point is ios 5 has no autorelease,release,retain.but we use #autoreleasepool in main class. pls give me a solution.
What is the use of autoreleasepool inside a method?
It seems you're using ARC (Automatic Reference Counting) this means you are not allowed to use autorelease, release and retain but the Compiler automatically includes these Statements at the correct Position. ARC is not a Runtime feature, but a compiler feature. that's why you nonetheless need the #autoreleasepool.
see also:
#autoreleasepool without ARC?
Related
When I run Xcode 4.5 , By default it is with ARC Off stage.But When we create Xcode project
Strong property comes instead of Retain.
1)If Strong and weak related to ARC , why is it coming in non-Arc project?
2)If Both strong and retain are same, If I change the keyword retain to strong in earlier
xcode versons for non-Arc projects,will it work correctly?
Yes, strong is just a synonym for retain when not using ARC - it's included in non-ARC projects by default to minimize the changes needed when converting between ARC and non-ARC, since retain doesn't work with ARC but strong works with both project types.
Also, yes, if you change it to retain, that won't break your code.
In addition to H2CO3 answer´s: xCode will not warn you about this situation. Indeed, if you are adding this class from ARC implemented project , remember to implement -(void)dealloc() method and release delegates in case of protocol implementation.
I'm making my first app and it's really confusing.
I am using ARC, and probably ALL of my potential leaks say:
"Object leaked: object allocated and stored in 'point' is not referenced later in this execution path and has a retain count of +1"
They are on almost any object I create using [[alloc] init].
Any suggestions about how to handle those? The app works fine, though.
Thanks.
Are you sure your project is actually set to ARC? Those types of analyzer warnings sound like it isn't. Is this a new project where ARC was automatically turned on for you or did you do the conversion for it yourself?
There isn't a way to actually tell the analyzer that you are ARC or aren't. It will just pick that up from the settings automatically.
I have this retained property declared like this:
#property (nonatomic, retain) NSMutableDictionary *codes;
then I synthesize this:
#synthesize codes;
I use the property like this:
self.codes = [NSMutableDictionary dictionary];
Then, I forget to say [codes release]; in my dealloc.
When I run Analyzer in XCode 4.3.2, this is not shown as an issue. My base SDK is iOS 5.1 and my compiler is Apple LLVM compiler 3.1
Why doesn't analyzer pick this up?
I imagine it's because the analyzer can't reliably detect retain/release issues across method/library boundaries.
You could conceivably pass ownership of your codes array to some external method or library which will release it later on for you. This would be bad practice because the receiving method should just retain it if it needs it, but I've seen this kind of thing done by inexperienced developers.
So you might see this in your class somewhere:
[SomeAPI takeThisArrayAndReleaseItLater:codes];
The analyzer has no way to know that your class is no longer responsible for releasing the array. To give you a warning would be incorrect, despite the fact that you are not following good memory management practices.
The analyzer is very good at only warning on real issues. I don't think I've ever seen a false-positive outside of betas builds, which is a good thing.
If you havent change anything from the configuration, whenver you target ios5+ you will automatically be using ARC (Automatic Reference Counting) which doesnt require you to release or retain.
The most disruptive change in iOS 5 is the addition of Automatic
Reference Counting, or ARC for short. ARC is a feature of the new LLVM
3.0 compiler and it completely does away with the manual memory management that all iOS developers love to hate.
This is a post by iOS Tutorial Team member Matthijs Hollemans, an experienced iOS developer and designer.
I am new to iOS 5 and ARC, so pardon my silly question.
If we use ARC in our project, does it mean that there wont be any memory leaks at all.
Is there a need to use Instruments for detecting memory leaks and NSZombies if we use ARC?
ARC will help you eliminate certain types of leaks, because you won't forget to release or autorelease single objects. For example, this type of error becomes impossible:
myLabel.text = [[NSString alloc] initWithFormat:#"%d", 17];
// oops, just leaked that NSString!
However, ARC will not eliminate leaks caused by retain cycles. It's still up to you to eliminate retain cycles, either by using weak references or by manually breaking the cycles before they become leaked. For example, as we start to use blocks more, block/self retain cycles become much more common. The Transitioning to ARC Release Notes discuss how to avoid these cycles using weak references.
No, that does not prevent memory leaks from happening. What happens in runtimes with reference counting, is that sometimes your code leaves dangling references, and then objects are not freed. It's still up to you to write good code.
If we use ARC in our project, does it mean that there wont be any memory leaks at all.
There may still be leaks -- In your program, and in the libraries you use. As well, ARC only applies to ObjC objects - you can easily leak any heap allocation which is not an objc object (e.g. malloc/new).
Is there a need to use Instruments for detecting memory leaks and NSZombies if we use ARC?
Yes. The previous response should detail why your program is not guaranteed to be free of these problems. Also, the compiler can get it wrong if you do silly things, and you can certainly cause problems if don't protect your data properly (e.g. concurrent execution).
I converted my project to using ARC and i works fine in iOS 5. But when running on the 4.3 simulator, i get a lot of these messages:
2011-10-16 12:23:29.915 iRoster[1604:1300b] * __NSAutoreleaseNoPool(): Object 0x5176e60 of class EKCalendar autoreleased with no pool in place - just leaking
I guess I could put a lot of #autoreleasepool around, but I had the impression that was optional. And the strange thing is that it only appears when running on 4.3
What should I do?
EDIT:
I have now placed some #autoreleasepool around and that reduced the messages a lot, so that seems to be the case.
If you have your own autorelease pools within your application logic that you manage yourself pre-ARC, you need to replace them with #autoreleasepool constructs, and the compiler will deal with them accordingly.
Converting to ARC doesn't necessarily mean your existing autorelease pools are no longer needed — you'll still need individual pools to contain temporary autoreleased objects in, for example, loops in other threads, so they won't spend forever in memory and/or start leaking in those threads. See this Apple documentation on using autorelease pools.