1.截取字符串

NSString *string =@"123456d890";
NSString *str1 = [string substringToIndex:5];//截取掉下标5之前的字符串
NSLog(@"截取的值为：%@",str1);
 NSString *str2 = [string substringFromIndex:3];//截取掉下标3之后的字符串
NSLog(@"截取的值为：%@",str2);

2.匹配字符串
从字符串(sd是sfsfsAdfsdf)中查找(匹配)字符串(Ad)

NSString *string =@"sd是sfsfsAdfsdf";
NSRange range = [string rangeOfString:@"Ad"];//匹配得到的下标
NSLog(@"rang:%@",NSStringFromRange(range));
string = [string substringWithRange:range];//截取范围内的字符串
NSLog(@"截取的值为：%@",string);

3.分隔字符串
根据字符串中的某个字符(A)来分割字符串

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adfsfsfs和dfsdf

*判断contents是否含有aaa

if([contents rangeOfString:@"aaa"].location !=NSNotFound)//_roaldSearchText
    {
      NSLog(@"yes");
    }else{
        NSLog(@"no");
    }