NSString的retainCount

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    NSString *str1 = [[NSString alloc] initWithString:@"111"];    //[NSString stringWithString:@"111"];    //@"111";    NSLog(@"str1%@:retainCount:%d", str1, [str1 retainCount]);

通过上面3种方式创建出来的NSString的retainCount 都是-1

不可变？静态常量区？(_NSCFConstantString *)？

NSString *temp = @"/tmp/scratch";
Note that, when creating a string constant in this fashion, you should avoid using anything but 7-bit ASCII characters. Such an object is created at compile time and exists throughout your program’s execution. The compiler makes such object constants unique on a per-module basis, and they’re never deallocated, though you can retain and release them as you do any other object.

// FROM http://www.cnblogs.com/Piosa/archive/2012/03/05/2380096.html

// -------------------------------------------------------------------------

// 结论I

// 普通NSString

// copy = retain [同一对象 retainCount+1,不可修改]

// mutableCopy [新对象 retainCount = 1,可修改]

// 可变NSMutableString

// copy = mutableCopy [新对象 retainCount = 1]

// copy != mutableCopy [copy=不可修改, mutableCopy=可修改]

// NSString @Property使用COPY,而不用retain

// 可以避免隐式NSMutableString被外部修改

// 结论II

// initWithString和直接赋值的NSString [retainCount = -1]

// 编译时就已经生成在静态常量区，并一直存在。