Conversion of a Core Data Store to/from JSON. The goal of this is to provide human-readable backup functionality for apps using Core Data without relying on any implementation details of Core Data.

Installation

Installation with the CDJSONExporter CocoaPod is the recommended way.

Otherwise, copy the code of CDJSONExporter (all .h and .m files in this repository) and NSData+Base64 to your project.

Usage

First, import: #import "CDJSONExporter.h".

To create export data:

NSData *export = [CDJSONExporter exportContext:appDelegate.managedObjectContext
                                 auxiliaryInfo:@{@"some key": someOptionalAuxiliaryInformation}];

This data can be written to a temporary file and shared with a UIDocumentInteractionController or used as an attachment in a mail compose view controller:

MFMailComposeViewController *mailer = ...;
// ...
[mailer addAttachmentData:export mimeType:@"application/json" fileName:@"backup.someAppBackup"];

To open the data later, you need to register your app as a handler for a document type / UTI with the extension someAppBackup. Afterwards, you can handle data with this extension in your app delegate:

- (BOOL)application:(UIApplication *)application 
            openURL:(NSURL *)url 
  sourceApplication:(NSString *)sourceApplication 
         annotation:(id)annotation {
    if([[url pathExtension] isEqualToString:@"someAppBackup"]) {
        NSData *jsonData = [NSData dataWithContentsOfURL:url];
        BOOL success = [CDJSONExporter importData:jsonData toContext:appDelegate.managedObjectContext clear:YES];
        if([[NSFileManager defaultManager] isDeletableFileAtPath:[url path]])
            [[NSFileManager defaultManager] removeItemAtURL:url error:NULL];
    }
}

Known Issues

The memory use of this code is not optimal. The main reason is the inability of Core Data to ever save invalid objects. This is usually a good thing, but prevents the code from persisting changes while importing.