如何在一对多关系中清除/重置所有 CoreData [英] How to clear/reset all CoreData in one-to-many relationship

问题描述

我正在使用 coreData，通过一对多的关系，我有一个文件夹实体和一个文件实体.一个文件夹可以有很多文件等等.

I am using coreData, with one -to-many realtionship, I have a folder entity and a file entity. A folder can have many files and so on.

所以，我有两个 ViewControllers，分别包含文件夹和文件的 FolderViewController 和 FileViewController.现在我有一个 modalView ，它可以从文件夹和文件视图控制器访问.在这个 VC 中，我有一个按钮可以重置所有数据.因此，当我单击此按钮时，我希望所有数据都应重置.

So, I have two ViewControllers, FolderViewController and FileViewController which contains folders and files respectively.Now I have a modalView , which is accesible from both folder and file viewcontroller. In this VC I have a button to Reset all Data. So when I click this I want all the data should reset.

我使用了这段代码，这个函数是用 appdelegate.m 编写的，并从我的 VC 中调用.

I used this code,this function is written in appdelegate.m and called from my VC.

- (void)resetToDefault
{
    NSError * error;
    // retrieve the store URL
    NSURL * storeURL = [[__managedObjectContext persistentStoreCoordinator] URLForPersistentStore:[[[__managedObjectContext persistentStoreCoordinator] persistentStores] lastObject]];
    // lock the current context
    [__managedObjectContext lock];
    [__managedObjectContext reset];//to drop pending changes
    //delete the store from the current managedObjectContext
    if ([[__managedObjectContext persistentStoreCoordinator] removePersistentStore:[[[__managedObjectContext persistentStoreCoordinator] persistentStores] lastObject] error:&error])
    {
        // remove the file containing the data
        [[NSFileManager defaultManager] removeItemAtURL:storeURL error:&error];
        //recreate the store like in the  appDelegate method
        [[__managedObjectContext persistentStoreCoordinator] addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error];//recreates the persistent store
    }
    [__managedObjectContext unlock];
    //that's it !

    NSLog(@"buttonReset Pressed");
}

因此，在关闭视图时单击 resetButton 后，出现此错误

So after clicking on resetButton when I close the View, I get this error

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Object's persistent store is not reachable from this NSManagedObjectContext's coordinator'

那么如何解决这个问题.

So how to solve this.

问候兰吉特

推荐答案

我已经解决了这个问题，下面是代码，

I have solved this problem, below is the code,

这个函数已经写在appdelegate.m中

This function has been written in appdelegate.m

- (void) resetApplicationModel
{
    NSError *error;
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"AppName.sqlite"];
    [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil];
    for (NSManagedObject *ct in [self.managedObjectContext registeredObjects]) {
        [self.managedObjectContext deleteObject:ct];
    }

    //Make new persistent store for future saves   
    if (![self.persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
        // do something with the error
    }  
}

在我的 SettingsViewController 中，我在以这种方式点击的重置按钮上调用它.

And in my SettingsViewController, I am calling this on resetbutton clicked in this way.

- (void)resetButtonclicked
{
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
        [appDelegate resetApplicationModel];  
}  

问候兰吉特.

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