IOS 生成六位随机数

- (NSString *)getVerificationCode
{
    NSArray *strArr = [[NSArray alloc]initWithObjects:@"0",@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"A",@"B",@"C",@"D",@"E",@"F",@"G",@"H",@"I",@"J",@"K",@"L",@"M",@"N",@"O",@"P",@"Q",@"R",@"S",@"T",@"U",@"V",@"W",@"X",@"Y",@"Z",nil] ;
    NSMutableString *getStr = [[NSMutableString alloc]initWithCapacity:5];
    for(int i = 0; i < 6; i++) //得到六位随机字符,可自己设长度
    {
        int index = arc4random() % ([strArr count]);  //得到数组中随机数的下标
        [getStr appendString:[strArr objectAtIndex:index]];
        
    }
    NSLog(@"验证码:%@",getStr);
    [strArr release];
    [getStr release];
    return getStr;
}