This article provides step-by-step instructions for setting up, maintaining, and ending data subscriptions for peer-to-peer asynchronous replication:

To set up a replication subscription in your app:

Syncing large documents can significantly impact sync performance:

Be cautious handling very large binary data, a deeply embedded document, or a very large document. Carefully consider using 

 instead of storing the data directly within a document object. For more information, see 

Before you can set up your subscription listener, initiate the replication process in your app. Initiating replication indicates that you're ready receive updates from remote peers, as well as send updates to subscribing remote peers.

To initiate replication, early in your app lifecycle, such as within 

AppDelegate.application(_:didFinishLaunchingWithOptions:)

You only need to call the following function once.

 in the top-most scope to ensure that as soon as your app starts, it automatically connects with the mesh network and remains active throughout your app's lifecycle.

Otherwise, the peer-to-peer connection may fail, resulting in remote peers becoming unable to send you updates in realtime.

In the top-most scope of your app, following the 

 method called in the previous step, set up a 

Once you've set up your subscription, your subscription query is automatically sent to all peers connected to the mesh network. If there are any data changes that match your criteria, Ditto automatically triggers your 

 callback function that performs followup actions and processes in your app.

For example, the following snippet demonstrates how to establish a 

 to listen for all updates to documents in the 

In order to prevent memory leaks, Ditto's built-in memory management mechanisms automatically cancels active subscriptions that are no longer needed or relevant.

Therefore, if you store the subscription object at a local scope within your code, once Ditto executes your 

 callback function, the subscription object may be removed from memory leading to unexpected behaviors. 

 on the subscription object you set up to establish your subscription:

For example, continuing with the previous example, the following snippet illustrates canceling the 

Best Practices for CRUD

Data Sync

linux_aarm_supported_version

android_supported_version

ipados_supported_version

ios_supported_version

windows_x64_supported_version

mac_supported_version

linux_x64_supported_version

Fields and Key-Values

Identifiers: Default and Custom

Collections

Version Control

Complex Structures

Evaluation Criteria

Relationships

Document Model

ditto

SDK v4.4 (and earlier)

Welcome to Ditto Docs - V4.4

Onboarding

Core Components

Sync Overview

Data Structures and Types

CRUD Fundamentals

Authentication and Initialization

Ditto Basics

Compatibility with Swift

Installing Swift SDK

Data Sync

Creating Subscriptions

Initiating Replication

Creating Subscriptions

Managing Lifetime Subscriptions

Canceling Subscriptions