What's the acceptable swift version for app submission?

Question

I have an existing app in the app store written using swift 3. For subsequent update will Apple reject my app because it's still in swift 3?

According to this link,

If your app is written in Swift, you can continue to submit apps in Swift 4 to the App Store and migrate individual modules to Swift 5 when you’re ready.

So means if swift version is less than 4 my app updates will get rejected? When will they stop accepting swift 4 apps?

Answer 1

Here is an excerpt from Apple:

Starting March 27, 2019, all iOS apps submitted to the App Store will need to be built with the iOS 12.1 SDK or later, and support the all-screen design of iPhone XS Max or the 12.9-inch iPad Pro (3rd Generation). All watchOS apps will need to support watchOS 5 and Apple Watch Series 4

This means that any submissions to App Store after March 27, 2019 requires iOS 12.1 SDK or later which I believe is available in Xcode 10.2 onwards. Xcode 10.2 doesn't have support for Swift 3. In essence, Apple stopped accepting applications written in Swift 3 after March 27, 2019.

The same principle would apply to Swift 4. Whenever they decide to up the minimum SDK requirement, it would force a minimum Xcode version which, in turn, would force minimum Swift version

Answer 2

From Apple:

Starting March 27, 2019, all iOS apps submitted to the App Store will need to be built with the iOS 12.1 SDK or later, and support the all-screen design of iPhone XS Max or the 12.9-inch iPad Pro (3rd Generation). All watchOS apps will need to support watchOS 5 and Apple Watch Series 4

This means that any submissions to App Store after March 27, 2019 requires iOS 12.1 SDK or later. According to Xcode wiki:, the included iOS SDK in Xcode 10.1 is iOS12.1. Furthermore, this link stated that for Xcode 10.1 the supported swift versions are 3.4.1, 4.1.5 and 4.2.1

Hence, it's alright submit apps using version 3.4.1, 4.1.5 or 4.2.1.

Couldn't find a consolidated list for swift version, Xcode SDK and iOS SDK. Will try to build one and post it here. And the frequency of the force upgrade of iOS SDK being implemented.

Answer 3

Based on this: https://developer.apple.com/documentation/xcode_release_notes/xcode_10_release_notes

Xcode 10 is the last release that will support Swift 3. Migrate your projects from Swift 3 code to Swift 4.2 syntax by opening the project and choosing Edit > Convert > To Current Swift Syntax

It will depend on Xcode and minimum iOS SDK version support. Probably Xcode 11 will not allow you to upload an ipa built from Swift 3 source at all.