ios - 为什么不分配这些 NSString 实例变量？

Question

第一次发帖。我之前正在阅读 Objective-C 教程，我看到他们制作了几个 NSString 实例变量，如下所示:

@implementation MyViewController {
NSString *stringOne;
NSString *stringTwo;
NSString *stringThree;
NSString *stringFour;
NSString *stringFive;
}

然后像这样简单地在 ViewDidLoad 中使用它们:

- (void)viewDidLoad
{
[super viewDidLoad];

stringOne = @"Hello.";
stringTwo = @"Goodbye.";
stringThree = @"Can't think of anything else to say.";
stringFour = @"Help...";
stringFive = @"Pheww, done.";
}

他们是如何在不实例化字符串的情况下做到这一点的？为什么这行得通？当然，在您可以简单地执行 stringOne= @"Hello. ";.

抱歉，如果这是一个愚蠢的问题，但我发现这些小事情让我很困惑。

谢谢，迈克

Answer 1

来自Apple String Programming Guide :

Creating Strings

The simplest way to create a string object in source code is to use the Objective-C @"..." construct:

NSString *temp = @"Contrafibularity";

Note that, when creating a string constant in this fashion, you should use UTF-8 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. You can also send messages directly to a string constant as you do any other string:

BOOL same = [@"comparison" isEqualToString:myString];