openswiftuiproject/openobservation

Backport implementation of Swift's Observation framework with access to `@_spi(SwiftUI)` APIs.

Purpose

The official Observation framework in Swift Toolchain doesn't ship with package.swiftinterface, preventing direct use of @_spi(SwiftUI) APIs. There are two solutions to this problem, but this project provides solution 2:

Manual workaround (not included): Construct a package.swiftinterface and add it to the toolchain (⚠️ No API stability, may break between toolchain versions)

OpenObservation approach (this project): Reimplement Observation framework, allowing OpenSwiftUI to import it via @_spi(OpenSwiftUI)

Implementation Status

The current implementation is aligned with Swift's release/6.1 branch implementation of the Observation framework.

Features

Full Observation framework implementation
Cross-platform support (macOS, iOS, tvOS, watchOS)
@Observable macro support
Thread-safe tracking
Pure Swift fallback for platforms without toolchain support

Installation

dependencies: [
    .package(url: "https://github.com/OpenSwiftUIProject/OpenObservation", from: "1.0.0")
]

Documentation

Comprehensive documentation is available on Swift Package Index.

Usage

import OpenObservation

@Observable
class Counter {
    var value: Int = 0
    
    func increment() {
        value += 1
    }
}

// Use with ObservationTracking
let counter = Counter()
withObservationTracking {
    print("Counter value: \(counter.value)")
} onChange: {
    print("Counter changed!")
}

Configuration

OPENSWIFTUI_SWIFT_TOOLCHAIN_SUPPORTED: Enable Swift toolchain runtime implementation (auto-detected)

- Config OPENSWIFTUI_SWIFT_TOOLCHAIN_PATH and OPENSWIFTUI_SWIFT_TOOLCHAIN_VERSION

OPENOBSERVATION_DEVELOPMENT: Development mode

License

OpenObservation code: MIT License
Code derived from Swift project: Apache License v2.0 with Runtime Library Exception

See LICENSE file.

Package Metadata

Repository: openswiftuiproject/openobservation

Default branch: main

README: README.md