如何在目标c中使用NSSortDescriptor按升序或降序对月份名称进行排序 [英] How to sort month name in ascending or descending order using NSSortDescriptor in objective c
问题描述
我需要使用 NSSortDescriptor 按升序或降序对月份和年份进行排序,我有一个数组
i need to sort the month and year in ascending or descending order using NSSortDescriptor i have one array
{
month = Dec;
year = 2017;
},
{
month = Oct;
year = 2017;
},
{
month = Jan;
year = 2018;
}
我曾经做过这个代码
NSSortDescriptor * sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"year" ascending:YES];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
yeardata = [NSMutableArray arrayWithArray:[yeardata sortedArrayUsingDescriptors:sortDescriptors]];
for (NSDictionary * dic in yeardata)
{
NSString * stryear = [dic objectForKey:@"year"];
NSString * strmonth = [dic objectForKey:@"month"];
[year addObject:[NSString stringWithFormat:@"%@ , %@",strmonth,stryear]];
}
我需要对数据进行排序2017 年 2 月2017 年 3 月2017 年 6 月2017 年 8 月2018 年 1 月
i need to sort data is Feb 2017 Mar 2017 June 2017 August 2017 January 2018
推荐答案
NSArray *array = @[@{
@"month":@"Dec",
@"year": @"2017",
},
@{
@"month":@"Oct",
@"year": @"2017",
},
@{
@"month":@"Jan",
@"year": @"2018",
}];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"MMM"];
NSArray *sorted = [array sortedArrayUsingComparator:^NSComparisonResult(NSDictionary * _Nonnull dict1, NSDictionary * _Nonnull dict2) {
NSDate *date1 = [dateFormatter dateFromString:dict1[@"month"]];
NSDateComponents *components1 = [[NSCalendar currentCalendar] components:NSCalendarUnitMonth fromDate:date1];
[components1 setYear:[dict1[@"year"] integerValue]];
NSDate *date2 = [dateFormatter dateFromString:dict2[@"month"]];
NSDateComponents *components2 = [[NSCalendar currentCalendar] components:NSCalendarUnitMonth fromDate:date2];
[components2 setYear:[dict2[@"year"] integerValue]];
NSDate *finalDate1 = [[NSCalendar currentCalendar] dateFromComponents:components1];
NSDate *finalDate2 = [[NSCalendar currentCalendar] dateFromComponents:components2];
return [finalDate1 compare:finalDate2];
}];
NSLog(@"Sorted: %@", sorted);
输出:
$>Sorted: (
{
month = Oct;
year = 2017;
},
{
month = Dec;
year = 2017;
},
{
month = Jan;
year = 2018;
}
)
那么逻辑是什么?
你不能用一个简单的 NSSortDescriptor
来做到这一点,因为你的月份是字母,而Dec"在Oct"之前按字母顺序排列,而不是时间".所以你需要创建一个可以简单比较的NSDate
.如果需要,您可以将该日期保存在数组的字典中,或者使用带有块的 sortedArrayUsingComparator:
.
So what's the logic?
You can't do that with a simple NSSortDescriptor
, because your month is in letter, and "Dec" is before "Oct" alphabetically order speaking, but not in "time" speaking.
So you need to create a NSDate
that can be simply compared.
You can save that date in the dictionaries of your array if needed, or use a sortedArrayUsingComparator:
with a block.
要颠倒顺序,块中最简单的方法:
To reverse the order, the easiest way in the block:
return [finalDate1 compare:finalDate2];
或
return [finalDate2 compare:finalDate1];
注意:finalDate1
/finalDate2
的构造方式可能不是最优的.
Note: The way of constructing finalDate1
/finalDate2
might be not optimum.
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