If your question is “How to update Xcode 10.1 to Xcode 10.2.1?” then you have come to the right place!
Recently Apple has updated Xcode to only work with the latest Mac OS Mojave (10.4.4), this means that developers who have old Macs won’t be able to update their OS and develop in Swift 5 using Xcode 10.2.1.
We at CodeWithChris however, found a solution to this dilemma!
Please do note however that this is a workaround. This is not in anyway supported by Apple as they have specifically set the new version of Xcode 10.2.1 for the latest OS only. We found that these steps work for us and we cannot guarantee if it will work for you.
Presenting: Installing/Updating Xcode 10.1 to Xcode to 10.2.1 on Mac OS High Sierra (10.13.6) or Mac OS Mojave (10.4.0)
Please note that we won’t be using the App Store to do this
Open in your browser https://developer.apple.com/download/more/
Log-in your Apple account and download Xcode 10.2.1 (or whatever is the latest)
Important!: If you don’t have Xcode installed yet also download and install 10.1 (you can do this by exacting the .xim file for Xcode 10.1 – it will automatically uncompress and have Xcode 10.1 installed and ready to use – you may rename the application to Xcode 10.1 to avoid confusion in the next parts)
After download completes (for Xcode 10.2.1) extract the .xim file (exacting the file will automatically uncompress and install that version of Xcode ready to use – you may rename the application to Xcode 10.2.1 if you wish as to avoid confusion).
The logo of Xcode should have an error icon on it, you can ignore this for now
Open the app directory (right click->show package contents) of your xcode 10.2.1 app
Navigate to Xcode 10.2.1.app/Contents/ and edit the file Info.plist, change the Minimum System Version to 10.13.6 (it should have 10.14.3 originally written on it), make sure to save.
Additionally, navigate to Xcode.app/Contents/Developer/Applications/Simulator.app/Contents/ edit Info.plist and also change the Minimum System Version to 10.13.6.
Step 3: (This is the reason why we need Xcode 10.1 installed)
Now go to your xcode 10.1 app directory (right click->show package contents) and copy the file xcodebuild located on Xcode 10.1.app/Contents/Developer/usr/bin/
Then, go to your xcode 10.2.1 app directory and overwrite the file xcodebuild located on Xcode 10.2.1.app/Contents/Developer/usr/bin/
Finally, restart your mac to reflect the changes made to the system.
And your done! you can now use xcode 10.2.1 in your your Mac! You will notice that the error icon is gone and you can now launch and use xcode10.2.1 for app development!