字符串拼接，替换，比较 的方法

字符串的拼接

NSString *string1 = @"iphone";

string1 = [string1 stringByAppendingString:@"123"];

    NSLog(@"%@",string1);

字符串替换

string1 =[string1 stringByReplacingOccurrencesOfString:@"ip" withString:@"pi"];

    NSLog(@"%@",string1);

 字符串比较

 NSComparisonResult result = [string1 compare:@"asdffggg"]

    if (result == NSOrderedAscending) {

        NSLog(@"nihao");

    }

原文：http://www.cnblogs.com/as5346/p/4471650.html