xcode NSCalendarUnit显示提前3个月

我正在计算当月的天数

      today = [NSDate date];

    NSLog(@"%@", today);

    //calculate how much days in current month

    NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSRange days = [cal rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:today];
    NSUInteger numberOfDaysInMonth = days.length;

    NSLog(@"%d Days in month:%i", numberOfDaysInMonth, NSMonthCalendarUnit);

   // end calculating

在日志中显示的是八月而不是五月

为什么会这样？我错过了什么

谢谢

2013-05-07 21:39:01.344 n计时器[89023:c07]2013-05-07 18:39:01+0000 2013-05-07 21:39:01.345 N时间[89023:c07]月内31天：8

答复:

谢谢@artur

这是一个正确的代码

    today = [NSDate date];

    NSLog(@"%@", today);

    //calculate how much days in current month

    NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    int units = NSMonthCalendarUnit;
    NSDateComponents *comps = [cal components:units fromDate:today];
    NSRange days = [cal rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:today];
    NSUInteger numberOfDaysInMonth = days.length;

    NSLog(@"%d Days in month:%i", numberOfDaysInMonth, comps.month);

   // end calculating

日志现在显示：

2013-05-07 22:25:04.855 NsTimer[89623:c07] 2013-05-07 19:25:04 +0000
2013-05-07 22:25:04.856 NsTimer[89623:c07] 31 Days in month:5

---

您将

NSMonthCalendarUnit

记录为整数（

%i

）。它只是枚举标志值，意外为8。要显示月数，应使用

[[calendar components:NSMonthCalendarUnit fromDate:today]month]

将其提取出来