---
title: swift-microservices/swift-persistence
framework: Swift Package Catalog
role: article
path: packages/swift-microservices/swift-persistence
---

# swift-microservices/swift-persistence

A transaction boundary that hands a unit of work exactly the repositories it may touch.

## The boundary

```swift public protocol Database<Scope>: Sendable {     associatedtype Scope: Sendable

func withTransaction<T: Sendable>(         _ operation: @Sendable (Scope) async throws -> T     ) async throws -> T } ```

When the closure returns, the transaction commits. When it throws, the transaction rolls back and the same error reaches the caller: no wrapper, so a use case catches the domain error its repository raised.

## The scope

The `Scope` is what the closure receives: repositories built on the transaction's connection, so everything inside the closure shares one transaction.

A use case declares the scope it needs as a protocol and takes `any Database` over it. The application's concrete scope conforms to every use case's protocol; a test supplies a scope of mocks. The use case is written once and sees neither.

```swift protocol CreatePostUseCaseScope {     var postRepository: any PostRepository { get } }

struct CreatePostUseCase<Scope: CreatePostUseCaseScope> {     let database: any Database<Scope>

func callAsFunction(input: CreatePostUseCaseInput) async throws {         try await database.withTransaction { scope in             try await scope.postRepository.create(title: input.title)         }     } } ```

## Drivers

| Package | Database | | --- | --- | | [swift-persistence-postgres](https://github.com/swift-microservices/swift-persistence-postgres) | PostgreSQL over PostgresNIO, with per-transaction session variables for row-level security |

A driver proves the commit and rollback contract in its own tests, against its own database.

## Requirements

Swift 6.3, macOS 15 or Linux.

## Development

```sh swift test swift-format lint --strict --recursive Sources Tests    # what the soundness check runs ```

## Contributing

Pull requests are welcome. Keep a change focused, and prove new behaviour with a test.

## License

MIT. See [LICENSE](LICENSE).

## Package Metadata

Repository: swift-microservices/swift-persistence

Default branch: main

README: README.md