ios - 如何在 iOS 中显示当前和前 6 个月的年份？

Question

我在一个项目中工作，我需要显示当前和过去 6 个月的年份。我正在使用以下代码来执行此操作。

for (int i=0; i< numberofMonths; i++) {

    NSString *index=[NSString stringWithFormat:@"%d",i+1];

    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *comps = [NSDateComponents new];
    comps.month = - (i+1);
    NSDate *date = [calendar dateByAddingComponents:comps toDate:[NSDate date] options:0];
    NSDateComponents *components = [calendar components:NSMonthCalendarUnit|NSYearCalendarUnit fromDate:date]; // Get necessary date 


    currentYear  = [components year];
    currentmonth=[components month];
    yearstring = [[NSString alloc]initWithFormat:@"%ld",currentYear];
    yearstring=[yearstring substringFromIndex:MAX((int)[yearstring length]-2, 0)];
    monthName = [[df monthSymbols] objectAtIndex:(currentmonth-1 )];
    NSString *string=[NSString stringWithFormat:@"%@, %@",monthName,yearstring];
    }

此代码适用于所有月份。但是当我将当前月份设置为一月/二月时。然后它确实给出了数组范围的错误。请指教

Answer 1

您的问题是，当您为 1 的 currentMonth 调用 [[df monthSymbols] objectAtIndex:(currentmonth-1 )]; 时，您最终会得到一个无效的月份编号。实现您所追求的目标的更简单的代码是-

int numberOfMonths=6;

NSDateFormatter *formatter=[[NSDateFormatter alloc]init];
[formatter setDateFormat:@"MMMM, YY" ];

NSCalendar *calendar = [NSCalendar currentCalendar];

NSDate *now=[NSDate date];

NSDateComponents *comps = [NSDateComponents new];

for (int i=-numberOfMonths; i< 1; i++) {

    comps.month = i;
    NSDate *newDate = [calendar dateByAddingComponents:comps toDate:now options:0];

    NSString *string=[formatter stringFromDate:newDate];
    NSLog(@"date=%@",string);
}