# Objective
On mobile devices, it's best to use the OS's native logging due to the
difficulty of accessing the console. This is already done for Android.
This is an updated version of
https://github.com/bevyengine/bevy/pull/4462.
## Solution
This PR uses Absolucy's
[tracing-oslog](https://github.com/Absolucy/tracing-oslog) ([ZLib
license](https://github.com/Absolucy/tracing-oslog/blob/main/LICENSE.md))
for iOS in order to use Apple's `os_log`.
## Testing
I ran `examples/mobile` with the logging from `examples/app/logs.rs` on
an iOS device, I then checked the logs could be filtered in the MacOS
Console.app.
## Changelog
- Change bevy_log to use Apple's os_log on iOS.
## Questions for Reviewers
It's worth noting that the dependency this adds hasn't had bug fixes
released in a few years, so we may want to consider one or more of:
1. a feature flag to opt-in, and it would also allow `os_log` on MacOS
2. merge as-is and have some (minor?) upstream bugs
3. hold off on this PR until a suitable alternative dependency arises
4. maintain our own implementation
## Future work
In a follow-up PR it might be good to make the `subsystem` field have a
better default value, like [this
one](https://github.com/bevyengine/bevy/blob/main/examples/mobile/bevy_mobile_example.xcodeproj/project.pbxproj#L363).
That value can be retrieved programmatically if we bind another system
API (For posterity in Swift this is `Bundle.main.bundleIdentifier`, but
the C/ObjC equivalent is likely easier to bind). This would almost
always be the correct value, while the current default is unlikely to
ever be correct.
---------
Co-authored-by: Dusty DeWeese <dustin.deweese@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Co-authored-by: François Mockers <francois.mockers@vleue.com>
6a39c33d49