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当一个或多个相关的NSManagedObject子类发生更改时,如何更新NSManagedObjects子类?

core-data ios

aaronium112 · 技术社区 · 10 年前

我想在“Day”中保持正确的表情。以下是我希望实现的目标:

每当“情绪”与 “天”。。。一天可以有很多情绪。
每当“情绪”从“日”中删除时,更新“日”的emoAvg
每当“情绪”的情绪属性发生变化时,更新“日”的情绪平均值。

enter image description here

我想将所有这些代码保存在模型层中,并且我已经能够通过调用以下代码将情绪与天联系起来,该代码在创建情绪时将一天附加到情绪上。

我还没能为“Day”和“Emotion”之间的多对多关系编写自定义访问器。我被Xcode 4.6.2卡住了,复制/粘贴自定义ObjectiveC访问器函数在这个版本中似乎不存在。

构建此代码的好方法是什么?

 - (void)setDate:(NSDate *)date
{
    [self willChangeValueForKey:@"date"];
    [self setPrimitiveValue:date forKey:@"date"];

    [self associateDay];

    [self didChangeValueForKey:@"date"];

}

-(void)associateDay
{
    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
    [dateFormatter setDateStyle:NSDateFormatterMediumStyle];

    NSDateComponents *dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:self.date];

    //Start of Day
    [dateComponents setHour:0];
    [dateComponents setMinute:0];
    [dateComponents setSecond:0];
    NSDate *startOfDay = [calendar dateFromComponents:dateComponents];
    //NSLog(@"Start of Day:       %@", [dateFormatter stringFromDate:startOfDay]);

    //End of Day
    [dateComponents setHour:23];
    [dateComponents setMinute:59];
    [dateComponents setSecond:59];
    NSDate *endOfDay = [calendar dateFromComponents:dateComponents];
    //NSLog(@"End of Day:         %@", [dateFormatter stringFromDate:endOfDay]);

    //Find all Day Entities that fall on the same calendar date
    NSPredicate *datePredicate = [NSPredicate predicateWithFormat:@"date > %@ AND date < %@", startOfDay, endOfDay];
    NSFetchRequest *fetchDays = [[NSFetchRequest alloc]initWithEntityName:@"Day"];
    fetchDays.predicate = datePredicate;
    NSManagedObjectContext *context = [(id)[UIApplication sharedApplication].delegate managedObjectContext];
    NSArray *daysFound = [context executeFetchRequest:fetchDays error:nil];

    if ([daysFound count] == 1)
    {
        Day *dayWithMatchingDate = [daysFound objectAtIndex:0];
        self.day = dayWithMatchingDate;
        NSLog(@"Found %d matching days",[daysFound count]);
    }

    if ([daysFound count] > 1)
    {
        NSLog(@"Found %d matching days...Something needs fixing",[daysFound count]);
    }

    if ([daysFound count] < 1)
    {
        NSLog(@"Found %d matching days...Making a new Day and associating it",[daysFound count]);
        NSManagedObjectContext *context = [(id)[UIApplication sharedApplication].delegate managedObjectContext];
        Day *newDay = [NSEntityDescription insertNewObjectForEntityForName:@"Day" inManagedObjectContext:context];
        newDay.date = self.date;
        self.day = newDay;
    }
}

2 回复 | 直到 10 年前

Mundi 10 年前

我认为,对 Day 作为数据模型的一部分。现有的日期属性应该足以用于选择、筛选和其他逻辑。

然而,你走在了正确的轨道上。关键是覆盖设置器。您需要重写以下setter Emotion 和 白天 (我的提示:创建类别论情感 Emotion+Additions 保持该代码与基本模型类分离)。

setEmotion 在里面 强烈的感情
removeEmotionsObject 在里面 白天
addEmotionsObject 在里面 白天

例如

-(void)removeEmotionsObject:(Emotion)value {
    NSSet *changedObjects = [[NSSet alloc] initWithObjects:&value count:1];
    [self willChangeValueForKey:@"emotions" 
        withSetMutation:NSKeyValueMinusSetMutation usingObjects:changedObjects];
    [[self primitiveEmotions] removeObject:value];
    [self didChangeValueForKey:@"emotions" 
        withSetMutation:NSKeyValueMinusSetMutation usingObjects:changedObjects];
}

有关这些访问者的详细信息,请参阅 relevant section 核心数据编程指南。

aaronium112 10 年前

我能够得到我要求的代码。然而,这是一个混乱的局面,我认为最好与NSNotificationCenter合作,观察相关对象的变化。这是有效的代码。我得给蒙迪一些支持,因为他帮助了我。

- (void)addEmotionsObject:(Emotion *)value
{
    NSSet *changedObjects = [[NSSet alloc] initWithObjects:&value count:1];

    [self willChangeValueForKey:@"emotions" withSetMutation:NSKeyValueUnionSetMutation usingObjects:changedObjects];

    [[self primitiveEmotions] addObject:value];

    [self calculateEmotionalAverage];

    [self didChangeValueForKey:@"emotions" withSetMutation:NSKeyValueUnionSetMutation usingObjects:changedObjects];
}

- (void)removeEmotionsObject:(Emotion *)value
{
    NSSet *changedObjects = [[NSSet alloc] initWithObjects:&value count:1];

    [self willChangeValueForKey:@"emotions" withSetMutation:NSKeyValueMinusSetMutation usingObjects:changedObjects];

    [[self primitiveEmotions] removeObject:value];

    [self calculateEmotionalAverage];

    [self didChangeValueForKey:@"emotions" withSetMutation:NSKeyValueMinusSetMutation usingObjects:changedObjects];
}



- (void)addEmotions:(NSSet *)value
{
    [self willChangeValueForKey:@"emotions" withSetMutation:NSKeyValueUnionSetMutation usingObjects:value];

    [[self primitiveEmotions] unionSet:value];

    [self calculateEmotionalAverage];

    [self didChangeValueForKey:@"emotions" withSetMutation:NSKeyValueUnionSetMutation usingObjects:value];
}



- (void)removeEmotions:(NSSet *)value
{
    [self willChangeValueForKey:@"emotions" withSetMutation:NSKeyValueMinusSetMutation usingObjects:value];

    [[self primitiveEmotions] minusSet:value];

    [self calculateEmotionalAverage];

    [self didChangeValueForKey:@"emotions" withSetMutation:NSKeyValueMinusSetMutation usingObjects:value];
}


-(void)calculateEmotionalAverage
{
    float emotionalTotal = 0;
    for (Emotion *emo in self.emotions)
    {
        if ([emo.emotion isEqualToString:@"Joy = 22"]){
            emotionalTotal += 22.0;
        }
        NSLog(@"%f",emotionalTotal);
    }
}