字符串长度适配

截取字符串长度。通常情况下，中文以及中文标点符号占2字节，ASIIC编码占1字节，如果规定字符长度不超过8位，可通过以下方法 

- (NSString *)nameLength:(NSString *)name{
    NSUInteger asciiLength = 0;
    NSMutableString *nameStr = [NSMutableString string];
    
    for (NSUInteger i = 0; i < name.length; i++) {
        unichar uc = [name characterAtIndex: i];
        asciiLength += isascii(uc) ? 1 : 2;
        NSString *strS = [name substringWithRange:NSMakeRange(i, 1)];
        if (asciiLength <= 16) {
            [nameStr appendString:strS];
        }else{
            [nameStr appendString:@"..."];
            return nameStr;
        }
    }
   
    return nameStr;
}