At this point, Swift is becoming mainstream for iOS app development.This blog post goes over challenges behind using the Swift programming language at a legacy project and how to overcome them. You’ll need to make fixes, but they’ll mostly be just that - fixes.Even though there is a plenty of Objective-C out there, if you’re not writing Swift now, you’re way behind as a software engineer and as an engineering organization. Just follow the rules at the top, and use an automated tool like Swiftify. Both previous projects started as app redesigns, and both failed. I know this because this is the 3 rd attempt. To summarize, this project would have been a failure if I’d tried to redesign the app while migrating. Import UIKit extension UIAlertController Final Thoughts Since all my alerts are of the form “something went wrong and there’s no action to take” the replacement is pretty simple: However, this also represented a good opportunity to test my first piece of Swift code - a Swift extension of UIAlertController. Increasing the minimum deployment target brought with it a whole bunch of deprecation errors (eg UIActionSheet and UIAlert). Updated the deployment target from 8.1 to 9.3 This produced more errors (warnings are errors now), which were then fixed.

My first step was to ensure the project contained zero warnings by enabling the build setting treat warnings as errors. Day 1 (Saturday 8 th) Upgraded to the latest Xcode build settings

Do one, then the other do not perform them simultaneously. I’ve performed quite a few code migrations over the years and one guarenteed way to fail is to change architecture and language at the same time.

Clean up your Swift to adhere to the latest standards.

Migrate your Objective-C files to Swift in the current Objective-C dialect (ie approximately zero refactoring).

Clean up your Objective-C code to adhere to the latest standards.

At a high level your best strategy to perform your migration in these steps If, like me you’re trying to make money out of your app then you’ll be looking to perform a staged migration from Objective-C to Swift.

Updated the deployment target from 8.1 to 9.3.

Upgraded to the latest Xcode build settings.

These are my ongoing notes chronicling this migration. Thanks to the iOSDevUK Conference and its attendees for the moral support to migrate almost wholesale to Swift. The earliest date within my iOS app Herd is May 3rd 2009.

Objective c to swift migration