Detect Unicode characters in NSString on iPhone

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 conver开发者_运维知识库t those characters into their UCS‐2 hexadecimal equivalents?

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

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 UTF-16 has superseded UCS-2.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

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.