automatic-ref-counting

问题 ARC forbids Objective-C objects in structs or unions despite marking the file -fno-objc-arc? Why is this so? I had the assumption that if you mark it -fno-objc-arc you don\'t have this restriction. 回答1: If you got this message try __unsafe_unretained. It is only safe, if the objects in the struct are unretained. Example: If you use OpenFeint with ARC the Class OFBragDelegateStrings says this error in a struct. typedef struct OFBragDelegateStrings { NSString* prepopulatedText; NSString*

问题 I\'m working on an iOS application that needs to play some sounds using the AVFoundation framework. The workspace structure in Xcode 4 contains two projects: Workspace The application itself (main project) A utility library After building the utility library, it results in a static library which is used in the main application as a framework. So, when trying to play a sound inside the main application by using the code below, it works as expected. NSString *resourcePath = [[NSBundle

问题 Just want to make sure that I got it right: Do I need to __unsafe_unretain objects that I don\'t own? If an object is __unsafe_unretained Do I need to use assign in the @property ? Does that mean that the object is not retained, and just refers to the object I assign to? When would I want to use it except of delegates? Is that an ARC thing or was it in use before? 回答1: The LLVM Compiler 3.0 introduces four new ownership qualifiers: __strong , __autoreleasing , __unsafe_unretained , and __weak

问题 approach 1: @interface MyController : UIViewController { UILabel *myText; } @property (nonatomic, strong) UILabel *myText; approach 2: @interface MyController : UIViewController @property (nonatomic, strong) UILabel *myText; approach 3: @interface MyController : UIViewController { UILabel *myText; } I have read some articles talking about this kind of stuff but I still do not really realize which approach I have to adopt. I also found that someone said approach 1 is a old way so I would like

问题 I am trying to understand the correct way of getting an NSString from a CFStringRef in ARC? Same for going the opposite direction, CFStringRef to NSString in ARC? What is the correct way to do this without creating memory leaks? 回答1: Typically NSString *yourFriendlyNSString = (__bridge NSString *)yourFriendlyCFString; and CFStringRef yourFriendlyCFString = (__bridge CFStringRef)yourFriendlyNSString; Now, if you want to know why the __bridge keyword is there, you can refer to the Apple

问题 I\'m trying to complete the puzzle. __strong is the default for all Objective-C retainable object pointers like NSObject, NSString, etc.. It\'s a strong reference. ARC balances it with a -release at the end of the scope. __unsafe_unretained equals the old way. It\'s used for a weak pointer without retaining the retainable object. __weak is like __unsafe_unretained except that it\'s an auto-zeroing weak reference meaning that the pointer will be set to nil as soon as the referenced object is

问题 When trying to use -retain , -release , and -dealloc while building my application using automatic reference counting in Xcode 4.2, I get an error like the following: Automatic Reference Counting forbids explicit message send of \'dealloc\' Why am I seeing this error? Are -retain , -release , and -dealloc no longer allowed under automatic reference counting? 回答1: Basically: When using ARC, it's all or nothing. Either the compiler is managing all of the retains/releases/deallocs for you, or it

问题 I recently started a new project using Automatic Reference Counting (ARC). When I assigned the contents of a CALayer: UIView* view = ... UIImage* image = ... view.layer.contents = image.CGImage I got an error Implicit conversion of a non-Objective-C pointer type \'CGImageRef\' to \'id\' is disallowed with ARC Simply casting the CGImageRef to id hides the error, but I was wondering if the ARC still functions correctly then? 回答1: You should really check out the ARC videos from WWDC 2011. They

问题 I\'ve read and heard since ARC was first announced that it was a compile-time thing and would be backwards-compatible with iOS 4. I have successfully refactored my project to ARC using Xcode 4.2\'s automatic refactoring, and when compiled against the iOS 5.0 SDK, it works fine. However, if I try to compile against my iOS 4.2 SDK, it fails at link time, missing the following symbols: _objc_retainAutoreleaseReturnValue _objc_autoreleaseReturnValue _objc_storeStrong _objc_retain _objc_release

问题 I\'m new to Xcode 4.2, and I\'m not yet fully up to speed on ARC. However, I did read that @autoreleasepool replaces the manual use of autorelease pools and does some special magic under the hood to play nice with ARC. Yet, when I start a new project in Xcode 4.2 specifically with the ARC option turned off I still get @autoreleasepool statements in the template code. What\'s the deal here? 回答1: From http://clang.llvm.org/docs/AutomaticReferenceCounting.html#autoreleasepool: @autoreleasepool