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

Answer 1

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 UTF-16 has superseded UCS-2.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