Question

我正在一个项目中工作，我需要显示当前和之前6个月的年份。我使用下面的代码来执行此操作。

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。但是当我把当前月份定为1月/ 2月时。然后它确实给出了数组范围的错误。请建议

Answer 1

您的问题是，当您将[[df monthSymbols] objectAtIndex:(currentmonth-1 )];的当前月份调用为1时，您的月份号码将无效。更简单的代码来实现你的目标是 -

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);
}

Answer 2

您可以使用NSDateFormatter从NSDate获取年份和月份字符串。不需要做所有这些马戏团。检查我的代码，这是你想要的吗？

  for (int i=0; i< 6; i++) {

    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

    NSDateFormatter *df = [NSDateFormatter new];
    [df setDateFormat:@"MMMM, yy"];
    NSString *dateString = [df stringFromDate:date];
        NSLog(@"%@ ",dateString);
}

如何在iOS中显示当前和之前6个月的年份？

2 个答案: