automatic-ref-counting

I have a code that compile without problems. It runs well on the iPhone simulator, but on my device, I get an EXC_BAD_ACCESS. This happens in a helper function to draw gradient. I followed this tutorial to do it. The code I have is as follows: - (void) drawRect:(CGRect)rect { CGContextRef context = UIGraphicsGetCurrentContext(); CGColorRef whiteColor = [UIColor whiteColor].CGColor; CGColorRef lightGrayColor = [UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0].CGColor; CGColorRef separatorColor = [UIColor colorWithRed:208.0/255.0 green:208.0/255.0 blue:208.0/255.0

I'm writing a tool which would benefit from knowing which of a class' instance variables are declared __weak . This information must exist somewhere at runtime, but is there any way of accessing it, documented or otherwise? (It's for a tool, so I don't care so much about it breaking with updates) Alright, here is a sample implementation, using a custom object implementation, that does a rudimentary check to see if an iVar is weak or not: BOOL iVarIsWeak(Class cls, Ivar ivar) { id classInstance = [cls new]; // our custom base class properly tracks reference counting, no weird voodoo id

I am new to iOS development in general and have never dealt with manual reference counting (retain, release, autorelease). As such I don't have a good understanding of what magic ARC is performing. I thought I understood until I was asked what type of ownership ( weak , strong , assign , etc) should be given to a readonly property pointing at an object, such as: @property (readonly,nonatomic) NSString* name; I read here Questions about a readonly @property in ARC that leaving off the strong / weak won't actually compile unless you specify a backing variable when you @synthesize the property; I

I've just stumbled over the following SO topic: Why should we copy blocks rather than retain? which has the following sentence: However, as of iOS 6 they are treated as regular objects so you don't need to worry. I was really confused by this assertion that is why I am asking: does this assertion really imply that Objective-C developers do not need to @property (copy) blockProperties or [^(...){...) {} copy] to copy blocks and their contents from stack to heap anymore? I hope the description I've made is clear. Please, be verbose. Similar questions Under ARC, are Blocks automatically copied

This question already has an answer here: capturing self strongly in this block is likely to lead to a retain cycle 7 answers I have reqest with block. But the compiler issues a warning "Capturing 'self' strongly in this block is likely to lead to a retain cycle" __weak typeof(self) weakSelf = self; [generalInstaImage setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:data[@"images"][@"low_resolution"][@"url"]]] placeholderImage:[UIImage imageNamed:@"Default"] success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) { NSLog(@"success");

I've recently come across an Apple document that shows the following property declaration for a block: @interface XYZObject : NSObject @property (copy) void (^blockProperty)(void); @end Also, this article states: Note: You should specify copy as the property attribute, because a block needs to be copied to keep track of its captured state outside of the original scope. This isn’t something you need to worry about when using Automatic Reference Counting, as it will happen automatically, but it’s best practice for the property attribute to show the resultant behavior. For more information, see

I have an iOS refactoring library that I want to work with and without the ARC compilation option. Is there a way to detect during compilation, like with an #ifdef , if ARC is available? Yes, you can use the following: #if __has_feature(objc_arc) ... #endif Even if you're using the latest version of LLVM, this will only evaluate to true if you're compiling with the -fobjc-arc option. 来源： https://stackoverflow.com/questions/7708267/check-for-arc-in-precompile

Will this lead to any sort of retain cycle? Is it safe to use? __block void (^myBlock)(int) = [^void (int i) { if (i == 0) return; NSLog(@"%d", i); myBlock(i - 1); } copy]; myBlock(10); myBlock = nil; Your code does contain a retain cycle, but you can break the retain cycle at the end of the recursion by setting myBlock to nil in the recursion base case ( i == 0 ). The best way to prove this is to try it, running under the Allocations instrument, with “Discard unrecorded data upon stop” turned off, “Record reference counts” turned on, and “Only track active allocations” turned off. I created a