UniformTypeIdentifiers Framework (PyObjC)

Warnings

• breaking PyObjC frequently drops support for older Python versions. PyObjC 12.0 dropped Python 3.9 support, and PyObjC 11.0 dropped Python 3.8 support. Version 12.1 corrected packaging metadata that incorrectly showed support for Python 3.9, which could lead to installation failures on that version.
  Fix: Ensure your Python environment meets the `requires_python` specification (>=3.10 for PyObjC 12.1) before upgrading PyObjC. Always check the PyObjC release notes or PyPI metadata for the target version.
• breaking PyObjC 11.1 aligned its core bridge with `clang`'s Automatic Reference Counting (ARC) documentation for initializer methods. Methods in the 'init' family now correctly steal a reference to `self` and return a new reference. This changed behavior for `[NSObject alloc]` proxies and can affect custom `init` implementations, potentially leading to crashes if old patterns are used.
  Fix: Review custom `init` implementations in Python subclasses of Objective-C objects. PyObjC 10.3 introduced a Pythonic `Class(...)` instantiation pattern that is generally safer.
• gotcha Version 10.3 initially broke `__init__` usage for Python subclasses of Objective-C classes, particularly when a user implemented `__new__` or when relying on PyObjC's `__new__` behavior. This was partially reverted in 10.3.1 to reintroduce `__init__` support when a user implements `__new__`.
  Fix: When subclassing Objective-C classes, implement Objective-C style `init` methods (e.g., `initWithFoo_:`). If overriding `__new__` in a Python subclass, ensure `__init__` is handled correctly, potentially using the pattern where `__init__` is only called if `__new__` returns an instance of the class itself. Update to 10.3.1 or later to mitigate this specific issue.
• gotcha `NSString` and `NSMutableString` are marked as 'final' in PyObjC versions 11.1 and later. Attempting to subclass these in Python will result in crashes due to special handling within PyObjC.
  Fix: Do not subclass `NSString` or `NSMutableString` in Python. If custom string behavior is needed, wrap an existing `NSString` or use Python's built-in string types.
• gotcha Installing PyObjC (especially from source or if binary wheels aren't suitable) requires Xcode or the Command Line Tools to be installed on macOS, including a compatible SDK for the target macOS version.
  Fix: Ensure Xcode or the Command Line Tools are installed via `xcode-select --install` before attempting installation, particularly if encountering compilation errors. Using an older SDK than the target macOS version can lead to build errors.
• gotcha PyObjC is a macOS-specific library and does not function on other platforms like iOS, Linux, or Windows.
  Fix: Only use PyObjC and its framework wrappers in macOS environments. For cross-platform development, consider alternative libraries or platform-specific conditional logic.

Install

• pip install pyobjc-framework-uniformtypeidentifiers Install latest version

Imports

• UniformTypeIdentifiers

  import UniformTypeIdentifiers

  The `UniformTypeIdentifiers` framework is imported as a module. Classes like `UTType` are attributes of this module, e.g., `UniformTypeIdentifiers.UTType`.

Quickstart

This example demonstrates how to import the `UniformTypeIdentifiers` framework, access system-declared UTIs, check type conformance, and create a UTI from a filename extension. Note that `Foundation` is often imported alongside PyObjC frameworks for basic Cocoa types like `NSURL`.

import UniformTypeIdentifiers
from Foundation import NSURL # Foundation is often implicitly needed or useful

# Get a system-declared UTI for an image
image_type = UniformTypeIdentifiers.UTType.image
print(f"Image UTI Identifier: {image_type.identifier}")
print(f"Image UTI Preferred filename extension: {image_type.preferredFilenameExtension}")

# Check conformance
text_type = UniformTypeIdentifiers.UTType.text
is_text_conforming_to_data = text_type.conformsToType_(UniformTypeIdentifiers.UTType.data)
print(f"Does text UTI conform to data UTI? {is_text_conforming_to_data}")

# Get a UTI from a filename extension
pdf_type = UniformTypeIdentifiers.UTType.typeWithFilenameExtension_("pdf")
if pdf_type:
    print(f"PDF UTI Identifier: {pdf_type.identifier}")