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 …