NSString保留计数 [英] NSString retain Count

问题描述

几天前我在做一个项目，我必须看看什么是字符串的保留计数.

Just couple of days i was working on a project and i have to see what is retain count of a string.

但是它总是返回我"2147483647"，为什么会这样?

But it always return me "2147483647", Why it is so?

签出此代码以自己检查.

Check out this code to check it yourself.

NSString *str = [[NSString alloc] initWithString:@"Hello World"];
NSLog(@"String Retain Count: %i", [str retainCount]); 

所以我的问题是为什么它不像其他对象一样返回1，为什么我得到"2147483647"

So my question is why it is not returning 1 like other objects return, why i am getting "2147483647"

先谢谢了.

推荐答案

编译器比您聪明.

看到@"Hello world"并想到啊！一个常量字符串！"

It sees @"Hello world" and thinks "Aha! A constant string!"

然后看到[[NSString alloc] initWithString:@"Hello world!"]并认为啊哈！一个用常量字符串创建的不可变对象！"

It then sees [[NSString alloc] initWithString:@"Hello world!"] and thinks "Aha! An immutable object created with a constant string!"

然后将它们都折叠为一个NSConstantString，该NSConstantString的retainCount为UINT_MAX，因此它永远不会被释放.

It then collapses both of them down into a single NSConstantString, which has a retainCount of UINT_MAX, so that it can never be released.

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