Detect Unicode characters in NSString on iPhone

Question

I am working on an SMS application for the iPhone. I need to detect if the user has entered any unicode characters inside the NSString they wish to send.

I need to do this is because unicode characters take up more space in the message, and also because I need to convert them into their hexadecimal equivalents.

So my question is how do I detect the presence of a unicode character in an NSString (which I read from a UITextView). Also, how do I then convert those characters into their UCS‐2 hexadecimal equivalents?

E.g 繁 = 7E41, 体 = 4F53, 中 = 4E2D, 文 = 6587

score 27 · Accepted Answer · answered Nov 10 '09 at 14:24

27

To check for only ascii characters (or another encoding of your choice) use:

[myString canBeConvertedToEncoding:NSASCIIStringEncoding];

It will return NO if the string contains non-ascii characters. You can then convert the string to UCS-2 data with:

[myString dataUsingEncoding:NSUTF16BigEndianStringEncoding];

or NSUTF16LittleEndianStringEncoding depending on your platform. There are slight differences between UCS-2 and UTF-16. UTF-16 has superseded UCS-2. You can read about the differences here:

http://en.wikipedia.org/wiki/UTF-16/UCS-2

answered Nov 10 '09 at 14:24

Jeremy Bower

576
4
7

@Jeremy Bower if i call [atext canBeConvertedToEncoding:NSUnicodeStringEncoding]; it always return yes regardless if i type a unicode char (Thai letter) or latin letter. – Ilker Baltaci Aug 07 '12 at 07:25
@Ilker Baltaci: That's because the characters can be converted to unicode. Unicode is a superset of ASCII and includes Thai characters. – Jeremy Bower Aug 31 '12 at 21:57

score 0 · Answer 2 · edited Jun 15 '15 at 12:57

I couldn't get this to work.

I has a html string with   NON BREAKING SPACE

</div>Great Guildford St/SouthwarkSt & nbsp;Stop:& nbsp; BM<br>Walk to SE1 0HL<br>
 "Great Guildford St/SouthwarkSt \U00a0Stop:\U00a0 BM",

I tried 3 types of encode/decode

// NSData   *asciiData   = [instruction dataUsingEncoding:NSUTF16BigEndianStringEncoding];                                          
// NSString *asciiString = [[NSString alloc] initWithData:asciiData 
//     encoding:NSUTF16BigEndianStringEncoding];

// NSData   *asciiData   = [instruction dataUsingEncoding:NSASCIIStringEncoding];                                           
// NSString *asciiString = [[NSString alloc] initWithData:asciiData 
//     encoding:NSASCIIStringEncoding];

//little endian
NSData   *asciiData   = [instruction dataUsingEncoding:NSUTF16LittleEndianStringEncoding];                                          
NSString *asciiString = [[NSString alloc] initWithData:asciiData
    encoding:NSUTF16LittleEndianStringEncoding];

none of these worked. They seemed to work as if I NSLog the string it looks ok

NSLog(@"HAS UNICODE  :%@", instruction); 
..do encode/decode
NSLog(@"UNICODE AFTER:%@", asciiString);

Which output

HAS UNICODE: St/SouthwarkSt  Stop:  BM
UNICODE AFTER: St/SouthwarkSt  Stop:  BM

but I happened to store these in an NSArray and I happened to call [stringArray description] and all the unicode was still in there

instructionsArrayString: (
    "Great Guildford St/SouthwarkSt \U00a0Stop:\U00a0 BM",
    "Walk to SE1 0HL"
)

So something in NSLog hides   but it shows up in NSArray description so you may think youve removed the Unicode when you haven't.

Will try another method that replace the characters.

Detect Unicode characters in NSString on iPhone

2 Answers2

Linked