核心数据表视图部分使用 NSSortDescriptor 按工作日排序 [英] Core Data Table View Section Sort by weekdays using NSSortDescriptor

问题描述

我目前正在尝试将我的对象数组按天顺序排序，以便它们可以按正确的顺序分组，即星期一、星期二、星期三，然后按开始时间分组.

I'm currently trying to sort my array of objects into day order so they can be grouped in the correct order i.e. Monday, Tuesday, Wednesday then by start time.

唯一的问题是我不知道如何做到这一点，我的代码目前看起来像这样:按字母顺序然后按时间排序:

Only problem is I can't figure out how to do this, my code currently looks like this: Which sorts alphabetically then by time:

NSString *sectionKey = nil;
switch (tab) {

case kByWeekA: {
NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"day" ascending:NO];
NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:@"starttime" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, sortDescriptor2, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
[sortDescriptor1 release];
[sortDescriptor2 release];
[sortDescriptors release];
sectionKey = @"day";
break;
}
case kByWeekB:{
NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"day" ascending:YES];
NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:@"starttime" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, sortDescriptor2, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
[sortDescriptor1 release];
[sortDescriptor2 release];
[sortDescriptors release];
sectionKey = @"day";
break;
}
default:
break;
}

请帮忙！

推荐答案

我看到两个解决方案:

1. 为您的排序描述符创建自定义比较，查看day"键并根据需要对它们进行排序.请参阅指定自定义比较 此处.
2. 将day"键设为整数，并按所需顺序对日期值使用枚举.

更新 2 选项 2 的示例代码:

UPDATE 2 Example code for option 2:

-将day"属性更改为数字(Int16)并添加瞬态(非持久性)dayName"字符串属性.

-Change the "day" attribute to a number (Int16) and add a transient (non-persistant) "dayName" string attribute.

-添加工作日的枚举:

typdef enum {
    kMonday,
    kTuesday,
    kWednesday,
    kThursday,
    kFriday,
    kSaturday,
    kSunday
} WeekDay;

-将托管对象的day"属性设置为 NSNumber 对象.例如:

-Set the "day" property of your managed objects to be NSNumber objects. For example:

object.day = [NSNumber numberWithInteger:kMonday];

-为瞬态dayName"属性实现 getter 函数:

-Implement the getter function for the transient "dayName" property:

- (NSString*)dayName {
    switch ((WeekDay)self.day.integerValue) {
        case kMonday:
            return @"Monday";
            break;
        case kTuesday:
            return @"Tuesday";
            break;
        case kWednesday:
            return @"Wednesday";
            break;
        case kMonday:
            return @"Monday";
            break;
        case kThursday:
            return @"Thursday";
            break;
        case kFriday:
            return @"Friday";
            break;
        case kSaturday:
            return @"Saturday";
            break;
        case kSunday:
            return @"Sunday";
            break;
    }
}

-在fetch请求中，按day"排序，使用dayName"作为section名key路径.

-In the fetch request, sort by "day" and use "dayName" as the section name key path.

更新
注意:选项 1 适用于对数组进行排序，但 Core Data 为不受支持的 NSSortDescriptor 选择器:weekdayCompare:"抛出NSInvalidArgumentException"异常:

选项 1 的示例代码:

Example code for option 1:

// category on NSString for custom comparison
@interface NSString (WeekdayComparison)
- (NSComparisonResult)weekdayCompare:(NSString*)otherDay;
@end
@implementation NSString (WeekdayComparison)
- (NSComparisonResult)weekdayCompare:(NSString*)otherDay {
    NSArray *weekDays = [NSArray arrayWithObjects:@"Sunday", @"Monday", @"Tuesday", @"Wednesday", @"Thursday", @"Friday", @"Saturday", nil];

    NSUInteger selfIndex = [weekDays indexOfObject:self];
    NSUInteger otherDayIndex = [weekDays indexOfObject:otherDay];

    if (selfIndex < otherDayIndex) {
        return NSOrderedAscending;
    }
    else if (selfIndex > otherDayIndex) {
        return NSOrderedDescending;
    } else {
        return NSOrderedSame;
    }
}
@end

要使用新的比较方法:

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"day" ascending:YES selector:@selector(weekdayCompare:)];
NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil];
[sortDescriptor release];

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