核心数据：使用图像预填充 SQLite 实体

Question

I am already pre-populating data for my application by first creating the database through core data, then populating that initialized file with SQLite Manager. Is it possible to pre-populate images in a SQLite table for use in core data as well?

My initial thought is to insert the images as a blob through SQLite Manager. Then based on this post , it looks like I would need to set the type to binary and import with UIImage initWithData: .

Is this doable, and if so, is this the appropriate method?

Answer 1

Pre-populating images to a SQLite database for use with Core Data turns out to be fairly trivial.

1. First configure your Core Data application, implementing your attribute to contain images as a "Binary" type. Build the application and navigate to your view utilizing Core Data within the application simulator. This will initialize the SQLite database as required for use with Core Data (assuming you've implemeted the persistentStoreCoordinator as follows).

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
    if (persistentStoreCoordinator != nil) {
        return persistentStoreCoordinator;
    }
    NSString *storePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"YourDBName.sqlite"];

    // Set up the store.
    // For the sake of illustration, provide a pre-populated default store.

    NSFileManager *fileManager = [NSFileManager defaultManager];
    // If the expected store doesn’t exist, copy the default store.
    if (![fileManager fileExistsAtPath:storePath]) {
        NSString *defaultStorePath = [[NSBundle mainBundle] pathForResource:@"YourDBName" ofType:@"sqlite"];
        if (defaultStorePath) {
            [fileManager copyItemAtPath:defaultStorePath toPath:storePath error:NULL];
        }
    }

    NSURL *storeUrl = [NSURL fileURLWithPath:storePath];
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, 
                             [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, 
                             nil];
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]];

    NSError *error;
    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) {
        // Update to handle the error appropriately.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        exit(-1);  // Fail
    }
    return persistentStoreCoordinator;
}

1. Navigate to the application data at "Users//Library/Application Support/iPhone Simulator/User/Applications/". If you sort the folder by "Date Modified," your application will have the latest date (assuming you haven't built any other applications in the mean time). Enter the application folder and the initialized < YourDBName.sqlite > will reside in the Documents folder. Copy the SQLite database to another location (like your desktop) and delete the original file (this is necessary to allow Core Data to reload the pre-populated SQLite database you are about to create).

2. Open < YourDBName.sqlite > with your favorite SQLite editor (the SQLite Manager plugin for Firefox is an adequate, and free, option). Add entries to your table, inserting any images as a "BLOB."

3. Within XCode add < YourDBName.sqlite > as an existing file. Core Data will copy this file to the application data folder the next time you launch your application if it does not already exist there (you deleted the original right?).

4. Access your pre-populated images within your code with [UIImage imageWithData:< DataObject >.< ImageAttributeName >

Answer 2

How big are your images going to be? If they are fairly large you may be better served by storing the image in the file system and keeping a reference to its location in core data.

If the images will always exist in your app then you can package them with your bundle. If not (eg a user can remove unwanted images) you may have to rely on pulling the images in on first use.