PyObjC DeviceCheck Framework

Warnings

• breaking PyObjC has dropped support for older Python versions. Version 12.0 removed support for Python 3.9, and version 11.0 removed support for Python 3.8. Users must ensure their Python environment meets the `>=3.10` requirement for PyObjC 12.1.
  Fix: Upgrade Python to version 3.10 or later. Consider using a virtual environment to manage Python versions.
• breaking PyObjC 11.1 changed how it models Objective-C's Automatic Reference Counting (ARC) for 'init' methods. Methods in the 'init' family now correctly 'steal a reference to self and return a new reference' in alignment with `clang`'s documentation. This change can affect applications relying on the previous, less accurate reference counting behavior, especially for singletons or in multithreaded contexts.
  Fix: Review custom Objective-C classes used with PyObjC, particularly those with 'init' methods, to ensure they correctly handle reference counts according to ARC guidelines. Update code that might have implicitly relied on previous PyObjC reference count handling quirks.
• gotcha The `DeviceCheck` framework, and thus `pyobjc-framework-devicecheck`, only functions on physical macOS/iOS devices and will not work when run on a simulator. Calls to `DCDevice.currentDevice().isSupported()` will return `False` on simulators.
  Fix: Test DeviceCheck functionality exclusively on actual hardware to ensure proper behavior and avoid unexpected `isSupported()` return values.
• gotcha Subclassing `NSString` or `NSMutableString` in Python using PyObjC is not supported and will lead to application crashes. These classes are treated as 'final' within the PyObjC bridge due to special internal handling.
  Fix: Avoid subclassing `NSString` or `NSMutableString` directly. If string manipulation or custom string behavior is required, consider wrapping standard Python strings or using other Cocoa collection types.
• gotcha Specific `NSData` and `NSMutableData` initialization methods, such as `dataWithBytesNoCopy:length:` or `initWithBytesNoCopy:length:`, should not be used with Python buffers. Cocoa might attempt to `free()` the buffer when the `NSData` object is released, which is incompatible with Python's memory management and can cause crashes. For methods like `dataWithBytesNoCopy:length:freeWhenDone:`, the `freeWhenDone` argument *must* be `False`.
  Fix: Always use `buffer(value)` to safely bridge Python bytes-like objects to `NSData` subclasses. If you must use methods that take `bytesNoCopy`, ensure the `freeWhenDone` parameter is explicitly set to `False`.

Install

• pip install pyobjc-framework-devicecheck Install stable version

Imports

• DCDevice

  from DeviceCheck import DCDevice

  Classes and functions from Objective-C frameworks are mapped directly to Python modules with the same name.
• AppHelper

  from PyObjCTools import AppHelper

  Required for running event loops in command-line scripts for asynchronous Objective-C calls.

Quickstart

This quickstart demonstrates how to access the current DCDevice, check if DeviceCheck is supported, and then generate a device token using an asynchronous Objective-C method. A Python function is used as the completion handler to process the token or any errors, and the PyObjCTools.AppHelper is used to manage the event loop necessary for asynchronous Objective-C calls in a script.

import objc
from DeviceCheck import DCDevice
from PyObjCTools import AppHelper
import Foundation # For NSData, NSError types

def device_check_completion_handler(token_data, error):
    """Objective-C completion handler for generateTokenWithCompletionHandler_."""
    if error:
        print(f"Error generating token: {error.localizedDescription()}")
    elif token_data:
        # NSData object from Objective-C can be converted to Python bytes
        python_token = token_data.bytes().tobytes()
        print(f"Successfully generated DeviceCheck token (first 10 bytes): {python_token[:10]}...")
    else:
        print("No token data and no error received.")
    AppHelper.stopEventLoop()

def main():
    device = DCDevice.currentDevice()

    if not device.isSupported():
        print("DeviceCheck is not supported on this device (e.g., simulator).")
        return

    print("DeviceCheck is supported. Generating token...")
    # Call the asynchronous Objective-C method with a Python callable as handler
    device.generateTokenWithCompletionHandler_(device_check_completion_handler)
    
    # Start the PyObjC event loop to process the asynchronous call
    print("Starting event loop (waiting for token or error)...")
    AppHelper.runEventLoop()
    print("Event loop stopped.")

if __name__ == "__main__":
    main()