Question

我的核心数据中有两个实体，名为“History”和“Favorite”。我想从“历史”实体中删除一些特定数据，如“达卡”。如何删除这个。提前谢谢。

Answer 1

希望它会对你有所帮助。

NSString* aType = @"History";
NSString *tp = @"Dhaka";

NSFetchRequest * request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:aType inManagedObjectContext:self.managedObjectContext]];
NSPredicate* predicate = [NSPredicate predicateWithFormat:@"(type == %@)",tp ]; //where type is the attribute
[request setPredicate:predicate];
NSArray* ar = [self.managedObjectContext executeFetchRequest:request error:nil];
NSLog(@"@@@@@@@@@@@@@  Data from DB  : %@",ar);
for(id anObj in ar){
    [managedObjectContext deleteObject:anObj];
}
[self.managedObjectContext save:nil];

predicate=nil;

Answer 2

试试这个：

   objAppDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
    NSManagedObjectContext *context = [objAppDelegate managedObjectContext];
    NSFetchRequest *request = [[NSFetchRequest alloc]initWithEntityName:@"History"];
    NSArray  *recordArray =[[NSArray alloc]initWithArray:[context executeFetchRequest:request error:nil]];
    objDataClass = [recordArray objectAtIndex:0];  // here objDataClass is a instance of DataClass derived from NSObject which define column name
    [context deleteObject:objDataClass]; // Delete particular data with index

    if ([context hasChanges])
    {
        [context save:nil];
    }
    else
    {
        NSLog(@"Object Deleted.....");
    }

希望它会对你有所帮助。：）

从目标c中的核心数据中删除特定实体的特定数据？

2 个答案: