核心数据表视图部分按工作日使用NSSortDescriptor进行排序

问题描述

我目前正在尝试将我的对象数组排序为天顺序，这样他们可以正确的顺序，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.

只有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;
}

请帮助！

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， 天键，并根据需要对其进行排序。请参阅指定自定义比较。


2. 将日键设置为整数，并按照所需顺序对日值进行枚举。

UPDATE 2 选项2的示例代码：

-Change将day属性赋予一个数字（Int16），并添加一个暂时（非持久）dayName字符串属性。

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

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;
    }
}

在获取请求中，并使用dayName作为节名称键路径。

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

UPDATE

注意：但是Core Data为'不支持的NSSortDescriptor选择器：weekdayCompare：'引发了一个'NSInvalidArgumentException'异常

UPDATE
Note: Option 1 works fine for sorting an array, but Core Data is throwing an 'NSInvalidArgumentException' exception for 'unsupported NSSortDescriptor selector: weekdayCompare:'

选项1的示例代码：

// 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

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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