CoreData中的数据处理的一些问题 增删改查

array 0 = (

    "<MsgForPush: 0x1d5c4260> (entity: MsgForPush; id: 0x1d5b0720 <x-coredata://A174ED32-E568-4FFE-AC00-CFD985E7D986/MsgForPush/p1> ; data: <fault>)",

    "<MsgForPush: 0x1d59a450> (entity: MsgForPush; id: 0x1d598eb0 <x-coredata://A174ED32-E568-4FFE-AC00-CFD985E7D986/MsgForPush/p2> ; data: <fault>)",

    "<MsgForPush: 0x1d59a500> (entity: MsgForPush; id: 0x1d5a04a0 <x-coredata://A174ED32-E568-4FFE-AC00-CFD985E7D986/MsgForPush/p3> ; data: <fault>)"

)

  直接取值 data:<fault>  

应该使用valueForkey来获取数据 

从数据库中删除数据

+ (void)deleteMsginfo

{

    NSManagedobjectContext *objectContext = [[AppDelegateAppDelegate] managedobjectContext];

     NSEntityDescription *entity = [NSEntityDescriptionentityForName:@"MsgForPush"inManagedobjectContext:objectContext];

    //查询数据库,搜索出该类

   NSFetchRequest *fetchRequest = [[NSFetchRequestalloc] init];

    [fetchRequestsetEntity:entity];

   NSError *error;

   NSArray *objects = [objectContext executeFetchRequest:fetchRequest error:&error];

   for (MsgForPush *searchin objects) {//清空该类数据

       Nsstring* alert_title = [search valueForKey:@"alert"];

       NSLog(@"delete title = %@",alert_title);

        [objectContextdeleteObject:search];

    }

   if ([objectContext hasChanges])

    {

       if (![objectContext save:&error])

        {

            NSLog(@"There was an error");

        }

    }

}

@月城眠  生日快乐 // 20130618115800

+(NSArray*)searchInTable:(Nsstring*)table ofAttribute:(Nsstring*)attr valued:(id)val inContext:(NSManagedobjectContext*)context//查找表table中属性attr的值为val的数据

{

    NSFetchRequest* fetchRequest = [NSFetchRequest fetchRequestWithEntityName:table];

    nspredicate *predicate = [nspredicate predicateWithFormat:@"(%K == %@)",attr,val];

    [fetchRequest setPredicate:predicate];

    NSError* error;

    NSArray* result = [context executeFetchRequest:fetchRequest error:&error];

    if (error) {

        Nsstring* info = [Nsstring stringWithFormat:@"查询表%@中属性%@值为%@时出现错误==%@",table,val,error.description];

        NSLog(@"%@",info);

    }

    return result;

}

//更新：直接修改对象，保存managedobjectContext就好

+ (BOOL)updateStatus:(Nsstring*)alert{

    NSManagedobjectContext* context = [AppDelegate AppDelegate].managedobjectContext;

    NSArray* read = [self searchInTable:@"MsgForPush" ofAttribute:dDBK_alert valued:alert inContext:context];

    NSLog(@"alert == %@",alert);

    NSLog(@"----read = %@",read);

    [read setValue:@"1" forKey:dDBK_status];

    NSError *error = nil;

    if (![context save:&error]) {

        NSLog(@"Unresolved error %@,%@",error,[error userInfo]);

        abort();

        return NO;

    }

    

    NSLog(@"update success");

    return YES;

}

////////////////////// 查重的问题～～～～～  

for (int i=0; i<array.count; i++)

    {

        //查重

        for (int j=i+1; j<array.count; j++)

        {

            NSDictionary *inquiryDic = [array objectAtIndex:i];

            NSDictionary* dic2 = [array objectAtIndex:j];

            if ([[inquiryDic objectForKey:@"alert"] isEqualToString:[dic2 valueForKey:@"alert"]])

            {

                [array removeObjectAtIndex:j];

                [objectContext delete:[array objectAtIndex:j]];

                j--;

            }

        }

    }

其它问题 更新中。。。。