問題描述

我正在使用 coreData，具有一對多的關系，我有一個文件夾實體和一個文件實體.一個文件夾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，我有兩個 ViewController，FolderViewController 和 FileViewController，它們分別包含文件夾和文件.現在我有一個 modalView，它可以從文件夾和文件 viewcontroller 訪問.在這個 VC 中，我有一個按鈕來重置所有數據.因此，當我單擊此按鈕時，我希望所有數據都應重置.

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.

我使用了這段代碼，這個函數寫在 appdelegate.m 中并從我的 VC 中調用.

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");
}

所以在我關閉視圖時單擊 resetButton 后，我收到此錯誤

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'

那么如何解決這個問題.

So how to solve this.

問候蘭吉特

推薦答案

這個問題我已經解決了，下面是代碼，

I have solved this problem, below is the code,

這個函數已經寫在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，我在以這種方式單擊的重置按鈕上調用它.

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

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

問候蘭吉特.

這篇關于如何以一對多關系清除/重置所有CoreData的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！