Question

我使用transient属性将核心数据对象分类到单独的表视图部分。它被称为'sectionIdentifier'。此属性的getter位于NSManagedObject subclass内，名为ToDoItem.m。问题是在应用程序执行期间，新添加的对象始终显示在“今日”部分下。在新推出应用程序后，所有对象都显示在预期的行下。专家用户告诉我，在设置新对象时，sectionIdentifier必须无效，但我不知道如何使其无效。这是我的NSManagedObject子类代码：

#import "ToDoItem.h"
#import "ToDoGroup.h"
#import "ToDoSubItem.h"


@implementation ToDoItem

@dynamic todoDescription;
@dynamic todoName;
@dynamic todoDueDate;
@dynamic sectionIdentifier;
@dynamic todogroup;
@dynamic todosubitems;



-(NSString *)sectionIdentifier{

    [self willAccessValueForKey:@"sectionIdentifier"];
    NSString *tmp = [self primitiveValueForKey:@"sectionIdentifier"];
    [self didAccessValueForKey:@"sectionIdentifier"];

    if (!tmp){

        NSDate *date = self.todoDueDate;
        NSDate *todayDate = [NSDate date];

        NSLog(@"date= %@",date);
        NSLog(@"todayDate = %@",todayDate);


        NSCalendar *calendar = [NSCalendar currentCalendar];
        NSInteger comps = (NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit);
        NSDateComponents *date1Components = [calendar components:comps fromDate:date];
        NSDateComponents *date2Components = [calendar components:comps fromDate:todayDate];
        date = [calendar dateFromComponents:date1Components];
        todayDate = [calendar dateFromComponents:date2Components];




        if([date
            compare:todayDate] == NSOrderedSame) {
            tmp = @"1";//TODAY
        }
        else if([date
                 compare:todayDate] == NSOrderedDescending){
            tmp = @"2";//OVERDUE
        }
        else if ([date
                  compare:todayDate] == NSOrderedAscending){
            tmp =@"0";//UPCOMING
        }
        NSLog(@"Tmp= %@",tmp);

        [self setPrimitiveValue:tmp forKey:@"sectionIdentifier"];

    }
    return tmp;

}


@end

欢迎任何帮助......

Answer 1

问题是部分标识符是从todoDueDate计算的和缓存，但在todoDueDate更改时不会自动更新。

DateSectionTitles/APLEvent.m Apple的示例代码显示了如何实现这样的自动更新。

在您的情况下，您应该将以下方法添加到托管对象子类 ToDoItem：

- (void)setTodoDueDate:(NSDate *)newDate
{
    // If the todoDueDate changes, the section identifier become invalid.
    [self willChangeValueForKey:@"todoDueDate"];
    [self setPrimitiveValue:newDate forKey:@"todoDueDate"];
    [self didChangeValueForKey:@"todoDueDate"];

    // Set the section identifier to nil, so that it will be recalculated
    // when the sectionIdentifier method is called the next time:
    [self setPrimitiveValue:nil forKey:@"sectionIdentifier"];
}

+ (NSSet *)keyPathsForValuesAffectingSectionIdentifier
{
    // If the value of todoDueDate changes, the section identifier may change as well.
    return [NSSet setWithObject:@"todoDueDate"];
}

使节标识符无效

1 个答案: