'Hello, World!' Sync

Intended to get you oriented, this article provides a streamlined process for integrating sync functionality within your app.

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Integrating Sync Functionality

Before you can begin syncing data offline, set up authentication and then start the sync process:

From the top-most scope of your app’s codebase, add the following to set up authentication and start syncing offline.

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Inserting Documents

Insert a document in your local Ditto store by calling the Execute API method on the store namespace with a local INSERT INTO query, specifying the document to insert.

For example, inserting a new document with a single field "color" set to "blue":

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Setting Up Store Observers

Establish a local listener, known as a store observer, for realtime monitoring and response to updates in your local Ditto store.

For example, you can set up a store observer to asynchronously display profile updates to end users when they modify their profiles.

To set up a store observer:

1. Call the Register Observer API method on the store namespace.

2. Include a local SELECT query specifying the document collection you want to watch and define a callback function to handle changes.

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Creating Subscriptions

Register a remote listener, known as a sync subscription, by calling the Register Subscription API method on the sync namespace.

For example, creating a subscription to sync updates made to documents in the cars collection with color set to blue:

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Takeaway

In Ditto, there is a clear distinction between traditional CREATE, READ, UPDATE, and DELETE (CRUD) database operations and data sync:

• To perform CRUD, you execute local data operations against store namespace.
• To perform sync, you execute remote data operations against the sync namespace.

To complete your understanding, the following graphic illustrates how sync subscriptions and store observers work together in practice:

1. Before you can sync offline, you must integrate sync functionality in your codebase. (See Integrating Sync Functionality)

2. Once integrated, you initiate a sync subscription request from your local Ditto store to remote peers. (See Creating Subscriptions)

The associated query specifying the data you want to watch then propagates to each end-user device connected within the mesh network:

When the data you’ve subscribed to changes on a remote peer — whether through insertions, updates, or deletions — the remote peer automatically syncs these delta changes to your local Ditto store over the mesh network:

Combining store observers with your sync subscriptions ensures that you receive updates from remote stores, enabling you to quickly respond in your app. (See Seetting Up Store Observers)