半角カナを全角カナにする。 NSString* strHankaku = @"ｱｲｳｴｵ"; NSString* strZenkaku = str.convertToZenkakukana; // strZenkaku → アイウエオ

NSString+Zenkakukana.h

@interface NSString(NSStringAddition)
- (NSString *)convertToZenkakukana;
@end

@implementation NSString(NSStringAddition)

- (NSString *)convertToZenkakukana
{
    NSMutableString *target =self.mutableCopy;

    for(int p = 0; p < [target length]; p++)
    {
        NSRange range = NSMakeRange(p, 1);
        NSString *moji = [target substringWithRange:range];
        
        @autoreleasepool
        {
            NSString* (^getZenkakuKanaWithHanaku)(NSString*) = ^(NSString* str) {
                if([str isEqualToString:@"ｦ"]) return @"ヲ";
                if([str isEqualToString:@"ｧ"]) return @"ァ";
                if([str isEqualToString:@"ｨ"]) return @"ィ";
                if([str isEqualToString:@"ｩ"]) return @"ゥ";
                if([str isEqualToString:@"ｪ"]) return @"ェ";
                if([str isEqualToString:@"ｫ"]) return @"ォ";
                if([str isEqualToString:@"ｬ"]) return @"ャ";
                if([str isEqualToString:@"ｭ"]) return @"ュ";
                if([str isEqualToString:@"ｮ"]) return @"ョ";
                if([str isEqualToString:@"ｯ"]) return @"ッ";
                if([str isEqualToString:@"ｰ"]) return @"ー";
                if([str isEqualToString:@"ｱ"]) return @"ア";
                if([str isEqualToString:@"ｲ"]) return @"イ";
                if([str isEqualToString:@"ｳ"]) return @"ウ";
                if([str isEqualToString:@"ｴ"]) return @"エ";
                if([str isEqualToString:@"ｵ"]) return @"オ";
                if([str isEqualToString:@"ｶ"]) return @"カ";
                if([str isEqualToString:@"ｷ"]) return @"キ";
                if([str isEqualToString:@"ｸ"]) return @"ク";
                if([str isEqualToString:@"ｹ"]) return @"ケ";
                if([str isEqualToString:@"ｺ"]) return @"コ";
                if([str isEqualToString:@"ｻ"]) return @"サ";
                if([str isEqualToString:@"ｼ"]) return @"シ";
                if([str isEqualToString:@"ｽ"]) return @"ス";
                if([str isEqualToString:@"ｾ"]) return @"セ";
                if([str isEqualToString:@"ｿ"]) return @"ソ";
                if([str isEqualToString:@"ﾀ"]) return @"タ";
                if([str isEqualToString:@"ﾁ"]) return @"チ";
                if([str isEqualToString:@"ﾂ"]) return @"ツ";
                if([str isEqualToString:@"ﾃ"]) return @"テ";
                if([str isEqualToString:@"ﾄ"]) return @"ト";
                if([str isEqualToString:@"ﾅ"]) return @"ナ";
                if([str isEqualToString:@"ﾆ"]) return @"ニ";
                if([str isEqualToString:@"ﾇ"]) return @"ヌ";
                if([str isEqualToString:@"ﾈ"]) return @"ネ";
                if([str isEqualToString:@"ﾉ"]) return @"ノ";
                if([str isEqualToString:@"ﾊ"]) return @"ハ";
                if([str isEqualToString:@"ﾋ"]) return @"ヒ";
                if([str isEqualToString:@"ﾌ"]) return @"フ";
                if([str isEqualToString:@"ﾍ"]) return @"ヘ";
                if([str isEqualToString:@"ﾎ"]) return @"ホ";
                if([str isEqualToString:@"ﾏ"]) return @"マ";
                if([str isEqualToString:@"ﾐ"]) return @"ミ";
                if([str isEqualToString:@"ﾑ"]) return @"ム";
                if([str isEqualToString:@"ﾒ"]) return @"メ";
                if([str isEqualToString:@"ﾓ"]) return @"モ";
                if([str isEqualToString:@"ﾔ"]) return @"ヤ";
                if([str isEqualToString:@"ﾕ"]) return @"ユ";
                if([str isEqualToString:@"ﾖ"]) return @"ヨ";
                if([str isEqualToString:@"ﾗ"]) return @"ラ";
                if([str isEqualToString:@"ﾘ"]) return @"リ";
                if([str isEqualToString:@"ﾙ"]) return @"ル";
                if([str isEqualToString:@"ﾚ"]) return @"レ";
                if([str isEqualToString:@"ﾛ"]) return @"ロ";
                if([str isEqualToString:@"ﾜ"]) return @"ワ";
                if([str isEqualToString:@"ﾝ"]) return @"ン";
                if([str isEqualToString:@"ｶﾞ"]) return @"ガ";
                if([str isEqualToString:@"ｷﾞ"]) return @"ギ";
                if([str isEqualToString:@"ｸﾞ"]) return @"グ";
                if([str isEqualToString:@"ｹﾞ"]) return @"ゲ";
                if([str isEqualToString:@"ｺﾞ"]) return @"ゴ";
                if([str isEqualToString:@"ｻﾞ"]) return @"ザ";
                if([str isEqualToString:@"ｼﾞ"]) return @"ジ";
                if([str isEqualToString:@"ｽﾞ"]) return @"ズ";
                if([str isEqualToString:@"ｾﾞ"]) return @"ゼ";
                if([str isEqualToString:@"ｿﾞ"]) return @"ゾ";
                if([str isEqualToString:@"ﾀﾞ"]) return @"ダ";
                if([str isEqualToString:@"ﾁﾞ"]) return @"ヂ";
                if([str isEqualToString:@"ﾂﾞ"]) return @"ヅ";
                if([str isEqualToString:@"ﾃﾞ"]) return @"デ";
                if([str isEqualToString:@"ﾄﾞ"]) return @"ド";
                if([str isEqualToString:@"ﾊﾞ"]) return @"バ";
                if([str isEqualToString:@"ﾋﾞ"]) return @"ビ";
                if([str isEqualToString:@"ﾌﾞ"]) return @"ブ";
                if([str isEqualToString:@"ﾍﾞ"]) return @"ベ";
                if([str isEqualToString:@"ﾎﾞ"]) return @"ボ";
                if([str isEqualToString:@"ﾊﾟ"]) return @"パ";
                if([str isEqualToString:@"ﾋﾟ"]) return @"ピ";
                if([str isEqualToString:@"ﾌﾟ"]) return @"プ";
                if([str isEqualToString:@"ﾍﾟ"]) return @"ペ";
                if([str isEqualToString:@"ﾎﾟ"]) return @"ポ";
                return str;
            };
            
            [target replaceCharactersInRange:NSMakeRange(p, 1) withString:getZenkakuKanaWithHanaku(moji)];
        }
    }

    return [target decomposedStringWithCompatibilityMapping];
}

@end