IOS Coredata UNIQUE 约束失败：

我正在尝试将数据插入 coredata 但出现错误，例如，

CoreData：错误：（1555）唯一约束失败：ZSIDETABLENAME.Z_PK

设想 ：-

首先：从 appdelegate.m 我将数据从 SQL 文件复制到文档目录的 sql 文件。

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }


   //  Create the coordinator and store

        NSString* from;
        NSString* to;
        NSArray* mainPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [mainPath objectAtIndex:0]; // Get documents folder
        /*VoiceRecords.plist file*/
        from=[[NSBundle mainBundle]pathForResource:@"News" ofType:@"sqlite"];
        to=[documentsDirectory stringByAppendingPathComponent:@"News.sqlite"];
        [[NSFileManager defaultManager]copyItemAtPath:from
                                               toPath:to error:nil];
        from=nil;
        to=nil;

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

    NSError *error = nil;
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
        /*
         Replace this implementation with code to handle the error appropriately.

         abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

         Typical reasons for an error here include:
         * The persistent store is not accessible;
         * The schema for the persistent store is incompatible with current managed object model.
         Check the error message to determine what the actual problem was.


         If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.

         If you encounter schema incompatibility errors during development, you can reduce their frequency by:
         * Simply deleting the existing store:
         [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]

         * Performing automatic lightweight migration by passing the following dictionary as the options parameter:
         @{NSMigratePersistentStoresAutomaticallyOption:@YES, NSInferMappingModelAutomaticallyOption:@YES}

         Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.

         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _persistentStoreCoordinator;
}

它工作正常。然后我尝试将用户输入的 url 保存在 mainviewcontroller.m 的 coredata 中。

- (void)feedParserDidFinish:(MWFeedParser *)parser {

        NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"IWorld"];
                fetchRequest.predicate = [NSPredicate predicateWithFormat:@"feedurl = %@", self.Feedlink];
        NSManagedObjectContext *context = [self managedObjectContext];

      if ([[context executeFetchRequest:fetchRequest error:NULL] count] == 0) {
                NSError *error = nil;

            NSPredicate *predicate=[NSPredicate predicateWithFormat:@"feedurl contains %@",check];
            [fetchRequest setPredicate:predicate];
              NSMutableArray *checkp = [[context executeFetchRequest:fetchRequest error:&error]mutableCopy];


            if (checkp.count<=0) {
                NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:@"IWorld" inManagedObjectContext:context];
                [newDevice setValue:self.Name forKey:@"name"];
                [newDevice setValue:self.WebsiteName forKey:@"websitename"];
                [newDevice setValue:self.Feedlink forKey:@"feedurl"];

                                   // Save the object to persistent store
                if (![context save:&error]) {
                    NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
                }
                    //Save value in lockbox

                NSArray *keys = [[[newDevice entity] attributesByName] allKeys];
                NSDictionary *dict = [newDevice dictionaryWithValuesForKeys:keys];

            }

        }


     NSFetchRequest *fetchrequestforside=[NSFetchRequest fetchRequestWithEntityName:@"Sidetablename"]; //Sidetablename is entity
    fetchrequestforside.predicate=[NSPredicate predicateWithFormat:@"feedurl = %@", self.Feedlink];
             NSManagedObjectContext *context = [self managedObjectContext];
    if ([[context executeFetchRequest:fetchrequestforside error:NULL] count] == 0) {
                    // Create a new managed object

                    NSError *error = nil;

                    NSPredicate *predicate=[NSPredicate predicateWithFormat:@"feedurl contains %@",check ]; //check is urlstring
                    [fetchrequestforside setPredicate:predicate];
                    NSMutableArray *checkp = [[context executeFetchRequest:fetchrequestforside error:&error]mutableCopy];


                    if (checkp.count<=0) //if coredata will find url then notstore in coredata else stored procedure
          {

                    NSManagedObject *newDevice1 = [NSEntityDescription insertNewObjectForEntityForName:@"Sidetablename" inManagedObjectContext:context];

                    if (self.Name)
                    {
                        [newDevice1 setValue:self.Name forKey:@"name"];


                    }
                    if (self.WebsiteName)
                    {
                        [newDevice1 setValue:self.WebsiteName forKey:@"websitename"];

                    }

                    if (self.Feedlink)
                    {
                        [newDevice1 setValue:self.Feedlink forKey:@"feedurl"];

                    }




                    NSError *error = nil;
                    if (![context save:&error]) {
                            NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]); // Getting error here through nslog //CoreData: error: (1555) UNIQUE constraint failed: ZSIDETABLENAME.Z_PK

                        }

注意：这一切都是第一次发生。第二次当我运行应用程序时一切正常。不知道问题出在哪里？

您在 sidetablename 表上遇到主键约束冲突。

因此，我相信您的问题在于您如何创建和复制种子数据库。

不幸的是，您没有提供该信息。因此，我只是猜测你是如何做到的。

我假设您使用 Mac 应用程序创建了数据库，或者在 iOS 模拟器中创建了数据库。然后，您将 sqlite 文件从创建它的位置复制到捆绑资源中。

由于自 iOS/OSX 7/10.9 以来 WAL 一直是默认模式，因此我假设您在 WAL 模式下创建了种子数据库。这意味着您可能错过了 -wal 和 -shm 文件。如果您指定任何数据属性应使用外部存储，那么您也会错过该数据。

创建要复制的种子数据库时，还需要复制 -shm/wal 文件，或者需要以回滚日志模式创建数据库，这将在文件中包含所有添加的数据。

您可以通过在添加持久性存储时设置以下选项来实现这一点（如果您已经使用选项，只需将此选项与其他选项合并即可）。

NSDictionary *options = @{NSSQLitePragmasOption:@{@"journal_mode":@"DELETE"}};
if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                                              configuration:nil
                                                        URL:storeURL
                                                    options:options
                                                      error:&error]) {
    // Handle error
}

这是在创建要复制到捆绑包的数据库时添加持久性存储的方式。它将确保所有内容都在实际的数据库文件中。

现在，运行代码创建种子文件后，您应该转到该目录并查看是否还有其他文件。最好的方法是在终端中。转到该目录并执行“ls -lat”，这将列出按时间排序的所有文件。

Caveat：SQLite 和 Core Data 都可以创建与 sqlite 文件一起使用的额外文件，具体取决于两个实体的配置。因此，一般来说，您应该将每个核心数据持久存储视为一个文件包。换句话说，您应该仅为核心数据存储创建一个单独的目录。这样，当 SQLite 或 core data 决定创建额外文件时，所有内容都被限制在一个目录中。

当您将文件复制到创建种子数据库的捆绑资源中时，您需要确保复制所有内容。

同样，部署时您应该将捆绑包中的所有内容复制到设备。

但是，您应该考虑使用这些方法，而不是使用文件系统NSPersistentStoreCoordinator...

/* Used for save as - performance may vary depending on the type of old and
   new store; the old store is usually removed from the coordinator by the
   migration operation, and therefore is no longer a useful reference after
   invoking this method
*/
- (NSPersistentStore *)migratePersistentStore:(NSPersistentStore *)store
                                        toURL:(NSURL *)URL
                                      options:(nullable NSDictionary *)options
                                     withType:(NSString *)storeType
                                        error:(NSError **)error;

/* copy or overwrite the target persistent store in accordance with the store
   class's requirements.  It is important to pass similar options as
   addPersistentStoreWithType: ... SQLite stores will honor file locks, journal
   files, journaling modes, and other intricacies.  Other stores will default
   to using NSFileManager.
 */
- (BOOL)replacePersistentStoreAtURL:(NSURL *)destinationURL
                 destinationOptions:(nullable NSDictionary *)destinationOptions
         withPersistentStoreFromURL:(NSURL *)sourceURL
                      sourceOptions:(nullable NSDictionary *)sourceOptions
                          storeType:(NSString *)storeType
                              error:(NSError**)error NS_AVAILABLE(10_11, 9_0);

因此，我相信，如果您正确创建数据库，然后将其完全正确地复制到资源包和应用程序中，那么您的问题就会消失。