unichar 和 NSString - 它们的互换性如何?

unichar and NSString - how interchangeable are these?(unichar 和 NSString - 它们的互换性如何?)

问题描述

有一个 NSString 方法 -characterAtIndex: 返回一个 unichar.

There is an NSString method -characterAtIndex: which returns an unichar.

• (unichar)characterAtIndex:(NSUInteger)index

我想知道这个显然不是 NSString 的 unichar 是否可以转换为 NSString 或馈送到 NSString 进行比较目的?

I wonder if this unichar, which obviously is not an NSString, can be converted into an NSString or feeded to an NSString for comparing purposes?

而且:NSString 内部是否只包含 unichar 项的数组?

And: Does an NSString internally just consist of an array of unichar items?

推荐答案

你有两个选择:第一个是一个类别，在 NSString 中添加一个 stringWithUnichar 方法:

You have two options: the first is a category adding a stringWithUnichar method to NSString:

@interface NSString (MNNSStringWithUnichar)
+ (NSString *) stringWithUnichar: (unichar) value;
@end


@implementation NSString (MNNSStringWithUnichar)

+ (NSString *) stringWithUnichar:(unichar) value {
     NSString *str = [NSString stringWithFormat: @"%C", value];
     return str;
}

@end

然后用

NSString *otherString = @"TestString";

NSString *str = [NSString stringWithUnichar:[otherString characterAtIndex:1]];

或者你可以直接这样:

NSString *str = [NSString stringWithFormat:@"%C",[otherString characterAtIndex:1]];

如果你想重复使用它，或者如果你只需要做一次，请选择类别，使用 stringWithFormat 示例！

Choose the category if you want to use it repeatedly, or if you only have to do it once, use the stringWithFormat example!!

不确定 NSString 的内部结构，但我猜它可能是包装了一个

Not to sure about the internals of NSString, but I'd guess it is probably wrapping a

unichar *

或一个 unichars 数组(如 C char *)

or an array of unichars (like a C char *)

unichar 只是一个 16 位的值，用于存储字符.与只有 8 位的 unsigned char 不同，它可以容纳 0-255 以上，因此它也可以容纳 16 位的 unicode 字符.NSString 是一个(集群)类[es]，其中包含一个 unichars 数组

A unichar is simply a 16bit value that is used to store a character. Unlike an unsigned char which is only 8 bits, it can hold more than 0-255, so it can hold unicode characters as well, which are 16bits. A NSString is a (cluster of) class[es] that contains an array of unichars

编辑

这里有几篇关于人们认为 NSString 是什么的文章:

Here are a few articles about what people think an NSString is:

http://cocoawithlove.com/2008/08/string-philosophies-char-arrays.html

http://www.reddit.com/r/programming/comments/6v1yw/string_philosophies_char_arrays_stdstring_and/

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