关于字符串的排序

转至http://www.cocoachina.com/bbs/read.php?tid=89685
很基础的东西。但是不看就容易忘。
1.截取字符串
NSString*string =@"sdfsfsfsAdfsdf";
string = [string substringToIndex:7];//截取掉下标7之后的字符串
NSLog(@"截取的值为：%@",string);
[string substringFromIndex:2];//截取掉下标2之前的字符串
NSLog(@"截取的值为：%@",string);

2.匹配字符串
NSString*string =@"sdfsfsfsAdfsdf";
NSRangerange = [stringrangeOfString:@"f"];//匹配得到的下标
NSLog(@"rang:%@",NSStringFromRange(range));
string = [string substringWithRange:range];//截取范围类的字符串
NSLog(@"截取的值为：%@",string);

3.分隔字符串
NSString*string =@"sdfsfsfsAdfsdf";
NSArray *array = [string componentsSeparatedByString:@"A"]; //从字符A中分隔成2个元素的数组
NSLog(@"array:%@",array); //结果是adffsfs和dfsdf

4.倒排字符串

NSString *string = @"asdf";
    NSMutableString *newString = [[NSMutableString alloc] initWithCapacity:string.length];
    for (int i = string.length - 1; i >=0 ; i --) {//注意这里是--以便从最后一个字符开始获取
        unichar ch = [string characterAtIndex:i];
        [newString appendFormat:@"%c"， ch];
    }