IOS - Unicode 无符号

我有一个用 C# 编写的函数，我想将其转换为 Objective-C。怎么做？

public static string UnicodeUnSign(string s)
{
    const string uniChars = "àáảãạâầấẩẫậăằắẳẵặèéẻẽẹêềếểễệđìíỉĩịòóỏõọôồốổỗộơờớởỡợùúủũụưừứửữựỳýỷỹỵÀÁẢÃẠÂẦẤẨẪẬĂẰẮẲẴẶÈÉẺẼẸÊỀẾỂỄỆĐÌÍỈĨỊÒÓỎÕỌÔỒỐỔỖỘƠỜỚỞỠỢÙÚỦŨỤƯỪỨỬỮỰỲÝỶỸỴÂĂĐÔƠƯ";
    const string koDauChars = "aaaaaaaaaaaaaaaaaeeeeeeeeeeediiiiiooooooooooooooooouuuuuuuuuuuyyyyyAAAAAAAAAAAAAAAAAEEEEEEEEEEEDIIIOOOOOOOOOOOOOOOOOOOUUUUUUUUUUUYYYYYAADOOU";

    if (string.IsNullOrEmpty(s))
    {
        return s;
    }

    string retVal = String.Empty;
    for (int i = 0; i < s.Length; i++)
    {
        int pos = uniChars.IndexOf(s[i].ToString());
        if (pos >= 0)
            retVal += koDauChars[pos];
        else
            retVal += s[i];
    }
    return retVal;
}

不诉诸核心基础：

#import <Foundation/Foundation.h>

int main (int argc, const char *argv[]) {
   NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

   NSString *unicodeCharacters = @"àáảãạâầấẩẫậăằắẳẵặèéẻẽẹêềếểễệđìíỉĩịòóỏõọôồốổỗộơờớởỡợùúủũụưừứửữựỳýỷỹỵÀÁẢÃẠÂẦẤẨẪẬĂẰẮẲẴẶÈÉẺẼẸÊỀẾỂỄỆĐÌÍỈĨỊÒÓỎÕỌÔỒỐỔỖỘƠỜỚỞỠỢÙÚỦŨỤƯỪỨỬỮỰỲÝỶỸỴÂĂĐÔƠƯ";

   NSString *decomposed = [unicodeCharacters decomposedStringWithCanonicalMapping];
   NSLocale *usLocale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US"] autorelease];

   NSString *cleaned = [decomposed stringByFoldingWithOptions:NSDiacriticInsensitiveSearch locale:usLocale];
   cleaned = [cleaned stringByReplacingOccurrencesOfString:@"đ" withString:@"d"];
   cleaned = [cleaned stringByReplacingOccurrencesOfString:@"Đ" withString:@"D"];
   NSLog (@"%@", cleaned);

   [pool drain];
   return 0;
}