取得NSDate实例各个字段的数字

 1     NSDate *now = [NSDate date];
 2     NSCalendar *calendar = [NSCalendar currentCalendar];
 3     
 4     //获取年、月、日、时、分、秒等组件
 5     NSDateComponents *dateComponents = [calendar components:NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond fromDate:now];
 6     NSLog(@"[%d]", dateComponents.year);    //年
 7     NSLog(@"[%d]", dateComponents.month);   //月
 8     NSLog(@"[%d]", dateComponents.day);     //日
 9     NSLog(@"[%d]", dateComponents.hour);    //时
10     NSLog(@"[%d]", dateComponents.minute);  //分
11     NSLog(@"[%d]", dateComponents.second);  //秒