iOS 切换到MRC环境下打印 retainCount 始终是－1或者一长串证书

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根据苹果的官方文档https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Protocols/NSObject_Protocol/Reference/NSObject.html

上面写着应该返回的是这个对象的UINT_MAX, 并且不会释放，这个UINT_MAX

最大二进制为（11111111111111111111111111111111）也是十六进制（0xffffffff）
如果你当成有符号数取补码后输出就得-1；
如果你当成无符号数就是最大数即：4294967295

2.在X64的机器上输出是9223372036854775807，int的最大值在I386的机器上输出是2.因为NSNumber的numberWithInteger产生的对象是属于autorelease pool

在帮助文档中

可以看到这么一句话：

The retainCount method does not account for any pending autorelease messages send to the receiver.

就是说retainCount 对于autorelease消息产生的的对象，并不可靠。

3.Do not use this method. (required) You should never use-retainCount, because it never tells you anything useful. 永远不要用这个方法，只要遵守alloc,neworcopy以及任何需要分配内存的时候调用release就可以了

参考文档：

http://www.friday.com/bbum/2011/12/18/retaincount-is-useless/。

4.iOS中的 NSString NSArray 这种iOS自身的对象貌似都做了一些优化，打印其retainCount的数值都是－1这种情况。

但是我们自己创建一个类

eg：Test.h

用它来创建的对象是完全和我们之前理解的retainCount预期值是相同的。

NSString *string = [[NSString alloc] init];

[string retain];

NSLog(@"string = %ld", (unsigned long)[string retainCount]);

NSLog(@"string = %lu", (unsigned long)[string retainCount]);

NSString *string2 = [[NSString alloc] initWithString:@"123"];

NSLog(@"string2 = %ld", (unsigned long)[string2 retainCount]);

NSLog(@"string2 = %lu", (unsigned long)[string2 retainCount]);

NSString *string3 = [NSString string];

NSLog(@"string3 = %ld", (unsigned long)[string3 retainCount]);

NSLog(@"string3 = %lu", (unsigned long)[string3 retainCount]);

NSString *string4 = [NSString stringWithFormat:@"123%@",@"123"];

NSLog(@"string4 = %ld", (unsigned long)[string4 retainCount]);

NSLog(@"string4 = %lu", (unsigned long)[string4 retainCount]);

Test *test = [[Test alloc] init];

[test retain];

[test release];

NSLog(@"test = %lu", (unsigned long)[test retainCount]);

以上代码的打印：

2016-12-20 17:29:17.103 acm[40218:510858] string = -1

2016-12-20 17:29:17.103 acm[40218:510858] string = 18446744073709551615

2016-12-20 17:29:17.103 acm[40218:510858] string2 = -1

2016-12-20 17:29:17.103 acm[40218:510858] string2 = 18446744073709551615

2016-12-20 17:29:17.104 acm[40218:510858] string3 = -1

2016-12-20 17:29:17.104 acm[40218:510858] string3 = 18446744073709551615

2016-12-20 17:29:17.104 acm[40218:510858] string4 = -1

2016-12-20 17:29:17.104 acm[40218:510858] string4 = 18446744073709551615

2016-12-20 17:29:17.104 acm[40218:510858] test = 1

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