ios - Core Data Fetch Request 在模拟器上运行，但在设备上不运行

Question

我正在从 AppDelegate 调用以下方法。 Fetch Request 在 iPad 设备上返回 0 条记录，请指教。记录在模拟器上正确返回。我已经确认传递的参数在设备和模拟器上都不是零。

+ (Movie    * ) movieWithID : (NSString * ) ID withObjectContext:(NSManagedObjectContext *) context

{

    Movie *movie= nil;

    NSFetchRequest *request =[[NSFetchRequest alloc]init];

     NSLog(@"ID : %@ Context : %@", ID,context);
     // Context and ID are not nil on both simulator and device

    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Movie" inManagedObjectContext:context];

    [request setEntity:entity];

    NSError *error =nil;

    NSArray * fetchResults = [context executeFetchRequest:request error:&error];
     //0 records are returned on the device
     //Correct number of records are returned on the simulator 


    if (entity && request) {

        NSLog(@"Fetch Count %d",[fetchResults count]);

    }

    else

    {

        NSLog(@"Entity is nil");

    }

    request.predicate = [NSPredicate predicateWithFormat:@"id like %@",ID];

     fetchResults = [context executeFetchRequest:request error:&error];

    if ([fetchResults count] > 1) {

        NSLog(@"Fetched Results > 1");

    }                              

    if (!fetchResults ) {
        NSLog(@"Fetch Failed");
    }

    else if ([fetchResults count]== 0) {

        NSLog(@"No movie results %@",error);

    }

    else if ([fetchResults count] ==1) {

        movie= [fetchResults lastObject];

    }

    return movie;

}

Answer 1

原因肯定是查询的店铺在iPad和模拟器上不一样。确保将任何准备好的 SQLite 存储正确复制到设备，并验证您尝试获取的数据确实存在。

测试此方法的一种方法是先在代码中插入数据。 - 然后您可以检查您的提取请求是否有效。