Question

我正在开发一个使用Parse.com服务器为每个PFUser存储PFUsers信息和类的应用程序。当我在线时，我可以将所有内容保存到服务器，但是当没有互联网连接时我也想使用该应用程序，这意味着当我离线时也可以保存它们。

我的应用很简单，我有：

LoginVC
Tableview与所有汽车“汽车为每个PFUSER”
ViewController“添加汽车”+

我在Parse.com Docs＆amp;当我们离线时，我发现了SaveEventually。

- (IBAction)save:(id)sender {


    PFUser*user = [PFUser currentUser];

    PFObject *CarsObject = [PFObject objectWithClassName:@"Cars"];
    CarsObject[@"makeandmodel"] = self.MakeModelTextfield.text;
    CarsObject[@"registrationnumber"] = self.CarImmatriculation.text;
    CarsObject[@"typeofCar"] = TypeACString;
    CarsObject[@"categoryofCar"] = CategoryString;
    CarsObject[@"User"] = user;

    MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
    hud.mode = MBProgressHUDModeDeterminate;
    hud.animationType = MBProgressHUDAnimationZoom;
    hud.labelText = @"Uploading";
    [hud show:YES];


    NSData *imageData = UIImageJPEGRepresentation(CarsImageView.image, 0.5);
    NSString *filename = [NSString stringWithFormat:@"%@.jpg",self.CarsImmatriculation.text];
    PFFile *imageFile = [PFFile fileWithName:filename data:imageData];
    [CarsObject setObject:imageFile forKey:@"CarImage"];



    [CarObject SaveEventually:^(BOOL success, NSError*error){
        [hud hide:YES];

        if (!error) {
            [self dismissViewControllerAnimated:YES completion:nil];
        }else {

            NSLog(@"ERROR SAVE");
        }

    }];


}

使用上面的代码我得到此错误[错误]：捕获“NSInternalInconsistencyException”，原因是“无法保存一个与新的未保存的PFFile有关系的PFObject”。因此它不起作用

所以我做了另一种方法，当用户登录时（当你在线时必须登录），我将所有值从服务器固定到localdatastore，如下所示：

- (void)FetchFromServerAtLogin{

    PFQuery*query = [PFQuery queryWithClassName:@"Cars"];
    [query whereKey:@"User" equalTo:[PFUser currentUser]];
    [query findObjectsInBackgroundWithBlock:^(NSArray*object, NSError*error){

        if (!error) {

            [PFObject pinAllInBackground:object block:nil];

        }else{

            NSLog(@"ERROR in Fetch From Server At login");
        }

    }];

}

我有一个Tableview，显示所有汽车，并从Localdatastore显示它们，所以它适用于此代码：

- (void)FetchFromDatabase{

    [self ShowAircraftCategory];

    PFQuery*query = [PFQuery queryWithClassName:@"Cars"];
    [query fromLocalDatastore];
    [query whereKey:@"User" equalTo:[PFUser currentUser]];
    [query whereKey:@"categoryofCars" equalTo:self.CategoryACString];
    [query findObjectsInBackgroundWithBlock:^(NSArray*object, NSError*error){

        if (!error) {
            NSArray*temp = [NSArray arrayWithArray:object];
            self.CarsArray = [temp mutableCopy];
            [self.tableView reloadData];

        }else{

            NSLog(@"ERROR in FetchFromDatabse");
        }

    }];

}

并且它起作用所以在这一点上我能够通过本代码获得我用VC创建的所有汽车：

- (IBAction)save:(id)sender {



    PFUser*user = [PFUser currentUser];

    PFObject *CarsObject = [PFObject objectWithClassName:@"Cars"];
    CarsObject[@"makeandmodel"] = self.MakeModelTextfield.text;
    CarsObject[@"registrationnumber"] = self.CarImmatriculation.text;
    CarsObject[@"typeofcar"] = TypeACString;
    AircraftObject[@"categoryofcar"] = CategoryString;
    AircraftObject[@"User"] = user;

    MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
    hud.mode = MBProgressHUDModeDeterminate;
    hud.animationType = MBProgressHUDAnimationZoom;
    hud.labelText = @"Uploading";
    [hud show:YES];


    NSData *imageData = UIImageJPEGRepresentation(CarImageView.image, 0.5);
    NSString *filename = [NSString stringWithFormat:@"%@.jpg",self.CarImmatriculation.text];
    PFFile *imageFile = [PFFile fileWithName:filename data:imageData];
    [CarsObject setObject:imageFile forKey:@"AircraftImage"];



    [CarsObject pinInBackgroundWithBlock:^(BOOL success, NSError*error){
        [hud hide:YES];

        if (!error) {
            [self dismissViewControllerAnimated:YES completion:nil];
        }else {

            NSLog(@"ERROR SAVE");
        }

    }];


}

我发现将Localdatastore保存到服务器的最后部分和唯一方式：使用按钮“LOGOUT”保存并取消将localDatastore中的所有PFObjects解压缩到服务器（如果没有互联网，则无法注销），如下所示：

-(IBAction)Logout:(id)sender{


    PFQuery*query = [PFQuery queryWithClassName:@"Cars"];
    [query fromLocalDatastore];
    [query whereKey:@"User" equalTo:[PFUser currentUser]];
    [query findObjectsInBackgroundWithBlock:^(NSArray*arrayOb, NSError*error){

    MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
    hud.mode = MBProgressHUDModeDeterminateHorizontalBar;
    hud.animationType = MBProgressHUDAnimationFade;
    hud.labelText = @"Uploading";
    [hud show:YES];


        if (error == nil) {
            NSArray*Cars = [NSArray arrayWithArray:arrayOb];
            [PFObject saveAllInBackground:Cars block:^(BOOL succeeded, NSError *error){
                [hud hide:YES];
                if (error == nil) {

                    [PFObject unpinAllObjectsInBackgroundWithBlock:nil];
                    [PFUser logOut];
                    [self performSegueWithIdentifier:@"Logout" sender:self];

                }

                else{

                    UIAlertView*alert = [[UIAlertView alloc] initWithTitle:@"LOGOUT ERROR  !" message:@"\n Please Connect to The Internet to SYNC with the Server all What you saved Locally  ! " delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
                    [alert show];
                }

            }];



        }else{

            UIAlertView*alert = [[UIAlertView alloc] initWithTitle:@"LOGOUT ERROR  !" message:@"\n Please Connect to The Internet to SYNC with the Server all What you saved Locally  ! " delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
            [alert show];
        }

    }];




}

**我的问题是“如果我在离线时退出应用程序而没有保存，我将失去ImageofCar的PFFile而我无法在本地数据库中恢复图像，剩下的就是”字符串“即：飞机的名称等...... **这个问题有一个解决方案???

谢谢

Answer 1

强制退出应用时，会在AppDelegate中调用此方法：

applicationWillTerminate:

您可以在那里注销您的用户。

但是，当应用程序处于非活动状态的时间过长时，它会进入非活动状态。你可以使用app delegate中的另一个方法来处理这种情况：

applicationWillResignActive:

有关您可以处理此类应用相关事项的更多地方，请参阅UIApplicationDelegate Protocol。

Answer 2

不幸的是，我认为PFFiles不会保留在本地数据存储区中。请参阅：related question

如何在Offline Parse.com中将图像PFFile保存在localdatastore中？

2 个答案: