从目标c中的核心数据中删除特定实体的特定数据？

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的数据，如“达卡”。如何删除这个。提前致谢。

Answer 1

希望它能帮助你。

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....."); 
    } 

希望它会帮助你。 :)