iPhone“计数”挫折？
好吧，我知道我一定在这里遗漏了一些明显的东西。这是示例代码（当在 viewDidLoad 块中执行时，它会默默地崩溃......没有错误输出到调试控制台）。
NSMutableArray *bs = [NSMutableArray arrayWithCapacity:10];
[bs addObject:[NSNumber numberWithInteger: 2]];
NSLog(@"%@", [bs count]);
[bs release];
我缺少什么？
哦...如果有人想知道，这段代码只是我试图弄清楚为什么我无法获得 NSMutableArray 的计数，而 NSMutableArray 在程序中的其他地方实际上很重要。
Okay, I know I must be missing something obvious here. Here's the sample code (which, when executed within a viewDidLoad block silently crashes... no error output to debug console).
NSMutableArray *bs = [NSMutableArray arrayWithCapacity:10];
[bs addObject:[NSNumber numberWithInteger: 2]];
NSLog(@"%@", [bs count]);
[bs release];
What am I missing?
Oh... and in case anyone is wondering, this code is just me trying to figure out why I can't get the count of an NSMutableArray that actually matters somewhere else in the program.
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[mutableArray count] 返回一个 NSUInteger。在你的 NSLog 中，你指定一个 %@，它需要一个 NSString。 Obj-C 不会自动将整数转换为字符串，因此您需要使用：
深入了解如何使用字符串格式。这是一个链接：
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html#//apple_ref/doc/uid/TP40004265-SW1
您还发布了已经自动释放的对象。根据经验，永远不要对对象调用release/autorelease，除非您自己也对其进行了alloc/retain/copy。大多数情况下，从其他类方法获取的对象已经为您自动释放，因此您不应该再次释放。
[mutableArray count] returns a NSUInteger. In your NSLog, you specify a %@, which requires a NSString. Obj-C does not automatically cast integers into strings, so you'll need to use:
Bone up on how to use string formatting. Here's a link:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html#//apple_ref/doc/uid/TP40004265-SW1
You're also releasing an object that already autoreleased. As a rule of thumb, don't ever call release/autorelease on an object, unless you yourself have also done an alloc/retain/copy on it. The majority of the time, objects you get from other class methods have already been autoreleased for you, so you shouldn't do another release.
最后不要释放！
arrayWithCapacity:10返回一个autoreleased 对象，这意味着它稍后会自动释放。自己释放它意味着它的计数将变为-1并且会发生不愉快的事情！ （正如您所发现的）作为一般规则，包含单词
alloc或copy的方法返回的对象必须由您释放，但其他人不能释放！ （当然，除非你先保留它们）Don't release it at the end!
arrayWithCapacity:10returns anautoreleased object, which means it will get released automatically later. Releasing it yourself means it's count will go to-1and unhappy things will happen! (As you have discovered)As a general rule, objects returned by methods containing the words
allocorcopymust be released by you, but no others! (Unless, of course, you retain them first)