相关疑难解决方法(0)

嗨,我是这个coredata的新手.我有两个实体CategoryList和ExpenseList.CategoryList包含两个属性
1.dates(nsdate)
2.categories(nsstring)
以及与ExpenseList的多个关系,关系名称为"expenseList"ExpenseList由1.amountSpent(float)组成.
我只是想知道了解coredata中的关系特征.当我试图创建一个nspredicate来按特定日期过滤数据时,它什么也没有返回.我只想过滤CategoryList实体中的类别属性内容以获取特定日期.这是我的代码

-(void) callingByDate
{


NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

NSEntityDescription *categoryL = [NSEntityDescription entityForName:@"CategoryList" inManagedObjectContext:managedObjectContext];

NSSortDescriptor *dateSort = [[NSSortDescriptor alloc]initWithKey:@"date" ascending:YES];

NSArray *sortDescriptors = [[NSArray alloc]initWithObjects:dateSort, nil];

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"dates == %@",date];



NSFetchRequest *dateFetch = [[NSFetchRequest alloc]init];



[dateFetch setSortDescriptors:sortDescriptors];

[dateFetch setEntity:categoryL];

[dateFetch setPredicate:predicate];



NSMutableArray *results = [[managedObjectContext executeFetchRequest:dateFetch error:nil] mutableCopy];

if([results count] > 0)

    NSLog(@"results found");

else

    NSLog(@"no results found");

}

当我在nslog区域执行此代码时,它显示"找不到结果".我无法弄清楚为什么.提前致谢

这是我的代码,以找到一天的结束和开始

-(NSDate *)beginningOfDay:(NSDate *)date;

 {

 NSDate *dat = [NSDate date];

 NSCalendar *cal …