Swift (Alpha)
The PowerSync Swift SDK is currently in an alpha release. It is not suitable for production use at this stage unless you’ve tested your use cases extensively. Breaking changes are still likely to occur.
Kotlin Multiplatform -> Native Swift SDK
This SDK is an extension of the Kotlin Multiplatform SDK, and utilizes the API tool SKIE to generate and publish a PowerSync SDK that can be used in a standalone Swift app. Further details about this configuration can be found in our blog here.
For the beta, we are moving away from this Kotlin-based architecture towards more Swift-native APIs. For the stable release, will are planning a fully native Swift SDK.
Demo App
We recommend the Supabase Todo List Demo app as a starting point for using the Swift SDK. See the README for details to run it.
SDK Features
-
Provides real-time streaming of database changes.
-
Offers direct access to the SQLite database, enabling the use of SQL on both client and server sides.
-
Operations are asynchronous by default, ensuring the user interface remains unblocked.
-
Supports concurrent database operations, allowing one write and multiple reads simultaneously.
-
Enables subscription to queries for receiving live updates.
-
Eliminates the need for client-side database migrations as these are managed automatically.
Installation
- Using
Package.swift:
-
Using Xcode:
- Follow this guide to add a package to your project.
- When searching for the package use https://github.com/powersync-ja/powersync-kotlin.git as the URL and include the exact version
1.0.0-BETA5.0
as shown below:
- Do the same for
power-sqlite-core-swift
using https://github.com/powersync-ja/powersync-sqlite-core-swift.git and choose a range between0.3.1
and0.4.0
as shown below:
Use the exact version for powersync-kotlin
as we are actively making changes to the Swift SDK which could result in breaking changes. The version history can be found here.
Getting Started
Before implementing the PowerSync SDK in your project, make sure you have completed these steps:
-
Signed up for a PowerSync Cloud account (here) or self-host PowerSync.
-
Configured your backend database and connected it to your PowerSync instance.
-
Installed the PowerSync SDK.
1. Define the Schema
The first step is defining the schema for the local SQLite database, which is provided to the PowerSyncDatabase
constructor via the schema
parameter. This schema represents a “view” of the downloaded data. No migrations are required — the schema is applied directly when the PowerSync database is constructed.
The types available are text
, integer
and real
. These should map directly to the values produced by the Sync Rules. If a value doesn’t match, it is cast automatically.
Example:
Note: No need to declare a primary key id
column, as PowerSync will automatically create this.
2. Instantiate the PowerSync Database
Next, you need to instantiate the PowerSync database — this is the core managed database.
Its primary function is to record all changes in the local database, whether online or offline. In addition, it automatically uploads changes to your app backend when connected.
Example:
3. Integrate with your Backend
Create a connector to integrate with your backend. The PowerSync backend connector provides the connection between your application backend and the PowerSync managed database.
It is used to:
-
Retrieve an auth token to connect to the PowerSync instance.
-
Apply local changes on your backend application server (and from there, to Postgres)
Accordingly, the connector must implement two methods:
-
PowerSyncBackendConnector.fetchCredentials
- This is called every couple of minutes and is used to obtain credentials for your app’s backend API. -> See Authentication Setup for instructions on how the credentials should be generated. -
PowerSyncBackendConnector.uploadData
- Use this to upload client-side changes to your app backend. -> See Writing Client Changes for considerations on the app backend implementation.
Example:
If you are using Supabase, you can use SupabaseConnector.swift as a starting point.
Using PowerSync: CRUD functions
Once the PowerSync instance is configured you can start using the SQLite DB functions.
The most commonly used CRUD functions to interact with your SQLite data are:
-
PowerSyncDatabase.get - get (SELECT) a single row from a table.
-
PowerSyncDatabase.getOptional - get (SELECT) a single row from a table and return
null
if not found. -
PowerSyncDatabase.getAll - get (SELECT) a set of rows from a table.
-
PowerSyncDatabase.watch - execute a read query every time source tables are modified.
-
PowerSyncDatabase.execute - execute a write (INSERT/UPDATE/DELETE) query.
Fetching a Single Item ( PowerSync.get / PowerSync.getOptional)
The get
method executes a read-only (SELECT) query and returns a single result. It throws an exception if no result is found. Use getOptional
to return a single optional result (returns null
if no result is found).
Querying Items (PowerSync.getAll)
The getAll
method executes a read-only (SELECT) query and returns a set of rows.
Watching Queries (PowerSync.watch)
The watch
method executes a read query whenever a change to a dependent table is made.
Mutations (PowerSync.execute)
The execute
method executes a write query (INSERT, UPDATE, DELETE) and returns the results (if any).
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