CDTIncrementalStore

An application can use CDTIncrementalStore to target Cloudant Sync as a persistent store for a Core Data application.

This document assumes you are familiar with Core Data. From the Apple documents:

The Core Data framework provides generalized and automated solutions to common tasks associated with object life-cycle and object graph management, including persistence.

It is this "persistence", which is provided by the Persistent Store, that we wish to add CDTDatastore as a backing store. The Incremental Store provides the hooks necessary to do this.

Thankfully, the user does not need to know these details to exploit CDTIncrementalStore from an application that uses Core Data.

Attention: CDTIncrementalStore is an experimental framework and might be unstable or change frequently, and might be discontinued at short notice. IBM does not guarantee or imply reliability, serviceability, or function of this framework. This framework is provided "AS IS", without warranty of any kind. IBM shall not be liable for any damages arising out of your use of this framework.

Getting started

CDTIncrementalStore is available through CocoaPods, to install it add the following line to your Podfile:

pod "CDTIncrementalStore"

Using in a Swift app

CDTIncremetalStore uses CDTDatastore and both are usable from Swift out of the box with a few small quirks. Install as per the instructions above, and import CDTIncrementalStore.h into your bridging header.

Note: There may be additional Swift considerations when using the CDTDatastore directly, please see cloudant sync documentation.

Core Data

If your application is not already using Core Data, see the Core Data documentation for the proper setup for a persistent store. This generally involves the initialization of a persistent store coordinator followed by a request to add a persistent store of a specific type to the persistent store coordinator.

This setup is commonly done in the application delegate, but could be done elsewhere. The common persistent store implementation is the NSSQLiteStoreType, which uses [SQLite] for persistent storage. To use CDTDatastore for Core Data persistent storage, specify [CDTIncrementalStore type] as the persistent store type, as follows:

#import <CDTIncrementalStore.h>

NSURL *storeURL = [docsDir URLByAppendingPathComponent:@"mystore"];
NSPersistentStoreCoordinator *psc = ...
[psc addPersistentStoreWithType:[CDTIncrementalStore type]
                  configuration:nil
                            URL:storeURL
                        options:nil
                          error:&error])];

The pathname of the storeURL may specify a suffix, e.g. ".cdtis", but none is required and no significance is given to the suffix. However, to avoid confusion, you should probably either change or remove the standard ".sqlite" suffix when converting from a sqlite store to a CDTIncrementalStore.

At this point you can use Core Data normally and your changes will be saved in the local CDTDatastore image.

Supported Features

The Cloudant Sync persistent store for Core Data supports the following features:

Save, fetch, update, and delete of Managed Objects to the on-device CDTDatastore.
Batch update requests
Asynchronous fetch operations
Schema migration

Unsupported Features

The following features of Core Data are currently not supported by the CDTIncrementalStore:

Predicates on string attributes using BEGINSWITH, ENDSWITH, LIKE, or MATCHES
Compound predicates using the NOT operator
Predicates on relationship attributes.

Example Application

An example application with detailed instructions on how to convert a CoreData application to use CDTIncrementalStore can be found in this GitHub repo. The application is based on Apple's iPhoneCoreDataRecipes and illustrates standard CoreData interactions with CDTIncrementalStore as well as replication to a remote Cloudant datastore.

Contributing to the project

See CONTRIBUTING.

License

See LICENSE

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