iOS判断一段字符串长度(汉字2字节)

-(NSUInteger)textLength: (NSString *) text{

    NSUInteger asciiLength = 0;

    for (NSUInteger i = 0; i < text.length; i++) {


        unichar uc = [text characterAtIndex: i];

        asciiLength += isascii(uc) ? 1 : 2;
    }

    NSUInteger unicodeLength = asciiLength;

    return unicodeLength;

}