UIAlertView不会显示在Appdelegate中

Question

我正致力于核心数据迁移。我试图处理异常时持久存储不匹配和应用程序崩溃。但在它崩溃之前，我想让用户知道（通过警报视图）他需要先卸载应用程序，然后重新安装它。我在persistentStoreCoordinator访问器方法中有警报视图的代码，但是alertview从不显示。

以下是代码：

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{

  if (__persistentStoreCoordinator != nil) {
    return __persistentStoreCoordinator;
}

NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"ExchangeMail.sqlite"];

NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

// Dictionary required to store the details of psc on the disk,
NSDictionary *sourceMetadata = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:NSSQLiteStoreType URL:storeURL error:&error];

// This BOOL value is required to check whether a migration is required or not.
BOOL pscCompatibile = [[self managedObjectModel] isConfiguration:nil compatibleWithStoreMetadata:sourceMetadata];
NSLog(@"Migration needed? %d", !pscCompatibile);


NSMutableDictionary *options = [[NSMutableDictionary alloc] init];
[options setValue:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption];
[options setValue:[NSNumber numberWithBool:YES] forKey:NSInferMappingModelAutomaticallyOption];

UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Non-matching Database File" message:@"The model configuration used to open the store is compatible with the one that was used to create the store. Please Uninstall the App and try again." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
[__persistentStoreCoordinator lock];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {

 //        dispatch_queue_t queue = NULL;
 //        queue = dispatch_get_main_queue();
 //        dispatch_async(queue, ^{
 //            [[NSFileManager defaultManager]removeItemAtURL:storeURL error:nil];
 //            
 //            [self.myAlertView show];
 //        });

    [self.myAlertView show];
    //exit(-1);
}

[__persistentStoreCoordinator unlock];


if(!pscCompatibile){
    isMigrationRequired = YES;
}

return __persistentStoreCoordinator;

}