PyObjC ExternalAccessory Framework

Warnings

• breaking PyObjC aggressively drops support for older Python versions. Version 12.0 dropped Python 3.9, and version 11.0 dropped Python 3.8. Ensure your Python environment meets the `requires_python` specification (currently `>=3.10` for v12.1).
  Fix: Upgrade your Python version to 3.10 or newer, or downgrade PyObjC to a compatible version if sticking with an older Python.
• breaking The core bridge's Automatic Reference Counting (ARC) behavior for initializer methods (those in the 'init' family) was updated in `v11.1` to align with `clang`'s documentation. This means PyObjC now correctly models that `init` methods steal a reference to `self` and return a new reference, potentially affecting custom `init` methods in Python subclasses.
  Fix: Review custom Python subclasses that override Objective-C initializer methods to ensure correct reference handling, especially when dealing with manually managed references or complex initialization patterns. Consult PyObjC's documentation on memory management.
• gotcha PyObjC is a macOS-specific library. It binds directly to Objective-C frameworks available only on Apple's macOS operating system. Attempts to install or run PyObjC code on Linux, Windows, or other platforms will fail with import errors or linker issues.
  Fix: Ensure your development and deployment environment is macOS. Use conditional imports or platform checks (`sys.platform == 'darwin'`) if your application needs to support multiple operating systems.
• gotcha Behavior around `__init__` and `__new__` methods in Python subclasses of Objective-C objects changed in `v10.3` and was partially reverted in `v10.3.1`. While `__init__` can now be used when a user implements `__new__`, code relying on the PyObjC-provided `__new__` still cannot use `__init__` for custom initialization logic.
  Fix: If implementing custom `__new__` in Python subclasses of ObjC objects, ensure `__init__` is correctly called and interacts with the PyObjC bridge as expected. For classes using PyObjC's default `__new__`, initialization logic must reside in other designated setup methods.

Install

• pip install pyobjc-framework-externalaccessory Install `ExternalAccessory` bindings

Imports

• ExternalAccessory

  import ExternalAccessory

  Framework symbols are typically imported directly under their framework name.

Quickstart

This quickstart demonstrates how to access the shared `EAAccessoryManager` and list currently connected MFi accessories. While this code runs, full interaction with `ExternalAccessory` (e.g., establishing communication sessions, receiving notifications) often requires an active Cocoa event loop and proper application lifecycle management, which is typically handled by `PyObjCTools.AppHelper` in more complex PyObjC applications.

import ExternalAccessory
import objc

def list_accessories():
    manager = ExternalAccessory.EAAccessoryManager.sharedAccessoryManager()
    accessories = manager.connectedAccessories()

    if accessories:
        print(f"Found {len(accessories)} connected accessories:")
        for acc in accessories:
            print(f"  - Name: {acc.name()}")
            print(f"    Model Number: {acc.modelNumber()}")
            print(f"    Manufacturer: {acc.manufacturer()}")
            print(f"    Serial Number: {acc.serialNumber()}")
            print(f"    Firmware Revision: {acc.firmwareRevision()}")
            print(f"    Hardware Revision: {acc.hardwareRevision()}")
            print(f"    Protocol Strings: {acc.protocolStrings()}")
    else:
        print("No MFi accessories connected.")

# Note: EAAccessoryManager typically requires an active runloop or
# an application context to correctly detect accessories and receive notifications.
# For simple scripting, you might need to run a console event loop.
# import PyObjCTools.AppHelper
# PyObjCTools.AppHelper.runConsoleEventLoop(installInterrupt=True, mode=objc.NSDefaultRunLoopMode, untilIdle=True)

if __name__ == '__main__':
    # This part runs the list_accessories function immediately.
    # In a full Cocoa app, this would be part of a delegate or controller.
    # For a simple script, it will just check at startup.
    list_accessories()