PyObjC Core

Warnings

• gotcha PyObjC is a macOS-specific bridge; it relies on macOS's Objective-C runtime and Cocoa frameworks. It will not work on Windows or Linux.
  Fix: Develop on macOS for applications leveraging PyObjC.
• breaking PyObjC frequently drops support for older Python versions (e.g., Python 3.9 dropped in v12.0, Python 3.8 in v11.0) to align with macOS SDKs and Python's own end-of-life cycles. Always check the 'requires_python' metadata for compatibility.
  Fix: Ensure your Python environment meets the minimum version requirements for the PyObjC release you are using.
• breaking PyObjC 11.1 introduced significant changes to how initializer methods (`init` family) handle reference counting to align with `clang`'s Automatic Reference Counting (ARC) documentation. This can change memory management behavior and potentially cause leaks or crashes in existing code that made assumptions about object lifecycle during initialization.
  Fix: Review code involving Objective-C initializer methods to ensure correct reference management in light of ARC semantics. Consult the PyObjC 11.1 release notes for details.
• gotcha While PyObjC 11 introduced experimental support for Python's PEP 703 (free-threading) feature in Python 3.13, it is still experimental. Use with caution, as it may not be stable or fully optimized for production environments.
  Fix: Avoid using free-threading with PyObjC in critical applications until it is officially declared stable. Test thoroughly if experimental features are enabled.
• gotcha `pyobjc-core` provides the fundamental bridge, but for most practical application development, you will also need specific framework bindings (e.g., `pyobjc-framework-Foundation`, `pyobjc-framework-AppKit`). The `pyobjc` meta-package installs `pyobjc-core` and many common frameworks and is generally recommended for ease of use.
  Fix: For full functionality, install `pyobjc` using `pip install pyobjc` rather than `pyobjc-core` alone.

Install

• pip install pyobjc-core Install core bridge only
• pip install pyobjc Install core bridge and common frameworks (recommended for most users)

Imports

• objc

  import objc

  The 'objc' module contains the core bridging functionality, including functions to look up Objective-C classes and fundamental constants.
• lookUpClass

  from objc import lookUpClass

  Core PyObjC functions and classes are exposed directly under the 'objc' module, not 'pyobjc_core'.
• python_class

  from objc import python_class

  Decorator to mark a Python class as an Objective-C class.

Quickstart

This quickstart demonstrates fundamental PyObjC interoperability, including converting Python types to Objective-C types, interacting with core Cocoa framework classes (like NSString and NSDate from Foundation), and defining Objective-C classes in Python. For this example to run, `pip install pyobjc` (which includes `pyobjc-core` and common frameworks like Foundation) is recommended.

import objc
from Foundation import NSString, NSDate, NSObject

# 1. Basic interoperability: Python string to Objective-C NSString
python_string = "Hello from PyObjC!"
objc_string = NSString.stringWithString_(python_string)
print(f"Python string: '{python_string}' (Type: {type(python_string)})\n")
print(f"Objective-C NSString: '{objc_string}' (Type: {type(objc_string)})\n")

# 2. Get current date as NSDate
current_nsdate = NSDate.date()
print(f"Current NSDate: {current_nsdate} (Type: {type(current_nsdate)})\n")

# 3. Define a Python class that inherits from an Objective-C class
@objc.python_class
class MyPythonObject(NSObject):
    def init(self):
        self = objc.super(MyPythonObject, self).init()
        if self is None: return None
        self.message = "I am a Python-backed Objective-C object!"
        return self

    # Expose a method callable from Objective-C (and Python)
    @objc.selector('myCustomMethod')
    def myCustomMethod(self):
        return self.message

# Create an instance and call the method
# Note: alloc().init() is the standard Objective-C way to create objects.
python_objc_instance = MyPythonObject.alloc().init()
print(f"Message from Python-backed ObjC instance: {python_objc_instance.myCustomMethod()}\n")