字符串记录方法

字符串分割

NSString *allString = @"12345678";

    NSMutableArray *resultArr = [NSMutableArray array];

    for (int i = 0; i < 21; i ++) {

        NSString *str2 = [allString substringWithRange:NSMakeRange(i,1)];

        [resultArr addObject:str2];

    }

    NSLog(@"resultArr:%@",resultArr);

[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