coredata 删除与更新

http://blog.csdn.net/rhljiayou/article/details/18037729

//删除
-(void)deleteData
{
    NSManagedObjectContext *context = [self managedObjectContext];
    NSEntityDescription *entity = [NSEntityDescription entityForName:TableName inManagedObjectContext:context];
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setIncludesPropertyValues:NO];
    [request setEntity:entity];
    NSError *error = nil;
    NSArray *datas = [context executeFetchRequest:request error:&error];
if (!error && datas && [datas count])
    {
for (NSManagedObject *obj in datas)
        {
            [context deleteObject:obj];
        }
if (![context save:&error])
        {
            NSLog(@"error:%@",error);
        }
    }
}
//更新
- (void)updateData:(NSString*)newsId  withIsLook:(NSString*)islook
{
    NSManagedObjectContext *context = [self managedObjectContext];
    NSPredicate *predicate = [NSPredicate
                              predicateWithFormat:@"newsid like[cd] %@",newsId];
//首先你需要建立一个request
    NSFetchRequest * request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:TableName inManagedObjectContext:context]];
    [request setPredicate:predicate];//这里相当于sqlite中的查询条件，具体格式参考苹果文档
//https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Predicates/Articles/pCreating.html
    NSError *error = nil;
    NSArray *result = [context executeFetchRequest:request error:&error];//这里获取到的是一个数组，你需要取出你要更新的那个obj
for (News *info in result) {
        info.islook = islook;
    }
//保存
if ([context save:&error]) {
//更新成功
        NSLog(@"更新成功");
    }
}