<span style="font-size:24px;">NSString *str =[NSString stringWithFormat:@"20|http://www.baidu.com"];
NSString *str1 = [str substringFromIndex:3];
NSLog(@"str1 = %@",str1);//输出为http://www.baidu.com
NSString *str2 = [str substringToIndex:2];
NSLog(@"str2 = %@",str2);//输出为 20
NSString *str3 = [NSString stringWithFormat:@"文艺青年"];//创建
NSString *newstr = [str3 stringByReplacingCharactersInRange:NSMakeRange(0, 2) withString:@"213"];//拼接213
NSLog(@"%@", newstr);</span>