首次启动时重置核心数据 [英] Reset core data at first launch

问题描述

出于某些原因，我必须在每次应用更新时更新我的​​核心数据模型。

For some reasons, I have to update my core data model at every app update.

问题是，每次更新时都会启动（仅在首次启动时）每次更新），我想重置我的模型，但我不知道如何继续。

The problem is, at first launch of every update (only at first launch of every update), I would like to reset my model but I don't know how to proceed.

有人曾经遇到过这种问题吗？

Is someone have ever had this kinf of problem ?

提前多多谢谢！

推荐答案

您是否启用了持久存储迁移？只要您只进行简单的模型修改，自动迁移就意味着您不需要重置数据。

Have you enabled Persistent Store migration? As long as you are only making trivial model modifications, automatic migration will mean you don't need to reset the data.

 NSError *error = nil;
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                                               configuration:nil
                                                         URL:storeURL
                                                     options:@{
                                                        NSMigratePersistentStoresAutomaticallyOption:@YES,
                                                        NSInferMappingModelAutomaticallyOption:@YES,
                                                        NSSQLiteAnalyzeOption:@YES,
                                                            }
                                                       error:&error])

如果有不同的理由清除您的模型，那么 NSUserDefaults 是可行的方法。您可以使用#define设置版本号，并在数字不同时重置持久存储，然后当您知道自己进行了需要空存储的更改时，可以增加#define：

If there's a different reason to clear your model, then NSUserDefaults is the way to go. You can use a #define to set a version number, and have the persistent store reset when the numbers are different, then when you know you've made a change that requires an empty store you can increment the #define:

#define kNukeTheCache 1000

...

    NSNumber *nukeNumber = [[NSUserDefaults standardUserDefaults] objectForKey:nukemeKey];

    if ((nukeNumber == nil) || (nukeNumber.integerValue < kNukeTheCache)) {
            [self deletePersistentStore:storeURL];
    }
    [[NSUserDefaults standardUserDefaults] setInteger:kNukeTheCache forKey:nukemeKey];
    [[NSUserDefaults standardUserDefaults] removeObjectForKey:totalNuke];
    [[NSUserDefaults standardUserDefaults] synchronize];


- (void)deletePersistentStore:(NSURL *)storeURL
{
    NSError *error = nil;
    [[NSFileManager defaultManager] removeItemAtURL:storeURL error:&error];
    if (error) { // Handle error }
}

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