NSString*string =@"sdfsfsfsAdfsdf";

string = [string substringToIndex:7];//截取掉下标7之后的字符串

[string substringFromIndex:2];//截取掉下标2之前的字符串

[string substringWithRang:NSMakeRange(0,3)]//截取下标0-3之间的字符串

2.匹配字符串

NSString*string =@"sdfsfsfsAdfsdf";

NSRangerange = [stringrangeOfString:@"f"];//匹配得到的下标

string = [string substringWithRange:range];//截取范围类的字符串

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