日期部分标题不起作用
我在按日期划分的表格视图上遇到问题。 我以苹果为例： DateSectionTitles
我不知道不在乎年份。我需要月日。 所以我这样调整我的代码：
在我的 CoreData 类中：
- (NSString *)sectionIdentifier {
[self willAccessValueForKey:@"sectionIdentifier"];
NSString *tmp = [self primitiveSectionIdentifier];
[self didAccessValueForKey:@"sectionIdentifier"];
NSLog(@"!Temp");
if (!tmp) {
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:[self timeStamp]];
tmp = [NSString stringWithFormat:@"%d", ([components month]*100) + [components day]];
[self setPrimitiveSectionIdentifier:tmp];
}
return tmp;}
在我的主控制器中的 titleForHeaderInSection 方法中：
NSInteger month = numericSection / 100;
NSInteger day = numericSection - (month * 100);
NSString *titleString = [NSString stringWithFormat:@"%d %d",day, month];
return titleString;
但是当我运行我的应用程序时，我收到此消息：
CoreData：错误：(NSFetchedResultsController) A 部分返回 nil 值节名称键路径“sectionIdentifier”。对象将被放置在未命名的部分
你知道为什么吗？ 感谢您的帮助 ！
I have a problem on a tableview with section by date.
I took the Apple example : DateSectionTitles
I don't care about year. I ust need month and day.
So I adapt my code like that :
In my CoreData class :
- (NSString *)sectionIdentifier {
[self willAccessValueForKey:@"sectionIdentifier"];
NSString *tmp = [self primitiveSectionIdentifier];
[self didAccessValueForKey:@"sectionIdentifier"];
NSLog(@"!Temp");
if (!tmp) {
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:[self timeStamp]];
tmp = [NSString stringWithFormat:@"%d", ([components month]*100) + [components day]];
[self setPrimitiveSectionIdentifier:tmp];
}
return tmp;}
And in my titleForHeaderInSection method in my main controller :
NSInteger month = numericSection / 100;
NSInteger day = numericSection - (month * 100);
NSString *titleString = [NSString stringWithFormat:@"%d %d",day, month];
return titleString;
But when I run my app I have this message :
CoreData: error: (NSFetchedResultsController) A section returned nil value for section name key path 'sectionIdentifier'. Objects will be placed in unnamed section
Do you know why ?
Thanks for your help !
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通常为 nsmanagedobject 编码瞬态属性的一个常见错误是人们忘记在数据模型文件 (xcdatamodeld) 中也“启用”瞬态属性。
One common mistake usually coding transient property for nsmanagedobject, is people forget to also "enable" transient property in the data model file (xcdatamodeld).
从逻辑上讲，如果在代码的这一行
[self timeStamp]返回无效的NSDate，就会发生这种情况。如果是这种情况，请检查 NSLog 语句。Logically, that would happen if at this line of your code
[self timeStamp]returns an invalidNSDate. Check withNSLogstatements if that is the case.