Updating mac software
While Apple is usually pretty good at making sure their i OS betas are compatible with the latest stable version of mac OS, sometimes they slip the ball.(For me, I recently had issues with both mac OS High Sierra 10.13.5 and mac OS High Sierra 10.13.6 with my i Phone running the i OS 12 developer beta 3.)In this case, you'll need to be running the latest beta version of mac OS, which, for the i OS 12 betas, would be for the mac OS Mojave 10.14 beta.Either that, or you'll need to downgrade your i Phone back to the latest stable release of i OS.Sometimes you might want to download a standalone installer instead of using Software Update.For example: Carefully read the download description before using a standalone installer.Instead, Apple has moved the system update mechanism to System Preferences, and in doing so has re-introduced the Software Update preference pane of old.The re-instated pane, which was discovered by a Reddit user, includes Advanced options previously found in the old Mac App Store preference pane, which it replaces.
It also helps you determine if your Mac is compatible with the related download.
If you have no interest in updating your Mac to the newest mac OS, the answer may be painfully obvious.
When you see the "A software update is required to connect to your i OS device.
To get the latest beta version of Xcode, you just need to visit developer.apple.com/download and sign in using your Apple ID (you don't need to be a developer to do this).
Once you're there, simply hit "Download" next to the latest Xcode beta, in my case, that's Xcode 10 beta 3.
Search for updating mac software:
If you don't want to jump on the latest mac OS beta but would like to stay on the i OS beta, then there's one more thing you can do — install the latest Xcode beta on your Mac.