# Dealing with API deprecations

Apple’s system APIs evolve like any other, new APIs are introduced and old ones are deprecated (and sometimes removed).

PyObjC has machinery to help you deal with API deprecations by providing Python level warnings for these API deprecations.

To enable warnings you need to do two things. First enable logging warnings for API deprecations:

    import warnings
    warnings.simplefilter("always", objc.ApiDeprecationWarning)

Then tell the bridge which API deprecations you want to get warnings about:

    import objc

    objc.options.deprecation_warnings = 1013

This fragment causes the bridge to emit a warning when you use an API that was deprecated in macOS 10.13 or earlier (but won’t warn about APIs deprecated in macOS 10.14 or later).

Warning

The machinery is already implemented, the metadata needed to emit the correct warnings is not present yet. This will change in future version of PyObjC.

## Example

The following script demonstrates the use of API deprecation warnings:

    1import objc
    2import warnings
    3warnings.simplefilter("always", objc.ApiDeprecationWarning)
    4objc.options.deprecation_warnings = 1014
    5
    6import Contacts
    7Contacts.CNPhoneNumber.alloc().init()

When you run this script it logs the following information:

    demoscript.py:7: ApiDeprecationWarning: -[CNPhoneNumber init] is a deprecated API (macOS 10.13)
      Contacts.CNPhoneNumber.alloc().init()