I keep downloading sample codes and many times it says "Unsupported Swift Version 3.x...Use Xcode 10.1 to migrate the code to Swift 4".
Why is it not possible to migrate to Swift 4 using Xcode 10.3 or Xcode 11 beta?
More importantly, I am using Swift 4.2 in my own Project that has several dependancies as well through Pods. If I don't upgrade to Swift 5.1 or later, it seems my own project would start getting such errors in Xcode 12 or so, correct? While I can convert my own code to Swift 5.1, I have no idea if dependencies such as SwiftyDropbox would migrate to Swift 5.1 so easily. What implications it would have for my project in future and what could I do to future proof my project in that case?
Ask Apple. The company has decided – certainly for good reasons – to migrate files only to the Current Swift Syntax. Feel free to create legacy system partitions with older versions of Xcode to migrate code step by step.
The grace period to update the Swift version is long enough to ensure a smooth transition. At least Xcode allows to use the 3 most recent Swift versions in the same project. However you are responsible to maintain the version control. Check the dependencies periodically for updates. If a dependency is not able to release an update within the grace period it's not much good.
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I provide a Swift framework for my customers.
It would only work in Xcode 10.3 (Or am I doing anything wrong?)
For other Xcode, it does have Swift compatibility issues.
So I am planning to release a series of versions of my framework so that a customer with a particular Xcode version can have the respective framework version of mine.
And it is pretty complex. Because for every release or bug fix I need to generate a bunch of versions.
I just want validation if this is the right approach.
How do I simplify this?
The compatibility issue you have is not from the version of the Xcode, is from the Swift version of the Framework. There is a difference.
In every project you can set the Swift version, but unfortunately you can't have more than one swift version per project. The current accepted ones are Swift 4, Swift 4.2 or Swift 5, as you can see in Xcode > Target > Build Settings:
Xcode 10.0 was the last version to support Swift 3 and is currently obsolete. I wouldn't create a framework version for it.
So, I would recommend you to either focus only on the latest Swift version and create a new Framework version every time a new Swift version appears (the most common approach), or start with the current three Swift versions and give them maintenance until the Swift version is deprecated.
My goal is to get the new Xcode 10.2 compile and run our projects that are build using Swift 3 and 4.2 (some cocoapods too) and since Xcode 10.2 comes with Swift 5, an unsupported swift error came up when trying to run the projects out of the box (this is expected):
The solution here is to use an older toolchain as stated on blogs like this, which i did.
All good so far. However, after installing the Swift 3 toolchain from Swift.org, compiling the project will bring the following error:
Command
/Library/Developer/Toolchains/swift-3.0-RELEASE.xctoolchain/usr/bin/swiftc
failed with exit code 1
I already deleted Derived Data folder, cleanup pods (my podfile) and reinstalled them, restarted Xcode and Mac multiple times.
Running xcrun -f swift and swift --version will indeed print the correct swift 3.0 toolchain
Yes, I know I could just stay with Xcode 10.1 and don't have these issues. Code migration to Swift 4 is also an option but we don't have the time at hand for now so I'm trying to workout this walkaround.
Please help me to resolve this issue, I'm completely stuck. Thanks in advance.
Xcode10.2 Release Notes
Swift 5 no longer supports the Swift 3 Package.swift tools-version.
Packages still on the Swift 3 Package.swift tools-version should
update to a newer tools-version. (41974124)
Swift 5.0
Source Compatibility As with Swift 4.2, the vast majority of sources
that built with the Swift 4.2 compiler should compile with the Swift
5.0 compiler.
However, the Swift 3 compatibility mode will not be supported in the
Swift 5 compiler. Swift 4.2 is the last release of Swift to support
Swift 3 mode. There are important changes to both the surface of the
language and the interior of its implementation in the releases
following Swift 3 that will be the basis of future (and lasting)
source and binary stability.
Using Swift 4.2.1 toolchain work for me.
But https://swift.org/download/#using-downloads tips:
To submit to the App Store you must build your app using the version of Swift that comes included within Xcode.
Upload to apple connect probably reject by apple.
I have a static library that I converter from old Swift to Swift 2.3 and later to Swift 3.0.
Now I need both version (2.3 and 3.0) of the library, but I forgot to take a backup of version 2.3. And I only have 3.0.
Is there a simple way to convert back from Swift 3.0 to Swift 2.3?
Simple, not really, but this will work.
If you don't have it, download XCode 7.3.1 from Apple
Open your library in the 7.3.1 version and correct whatever errors appear
Migrate the corrected code from step 2 into XCode 8.2 or lower (8.3 will not support Swift 2.3)
As mentioned in the comments, maintaining your code in a version control system will spare you problems like this in the future, and is generally just a good idea.
You don't even need to set up your own system, since git is part of MacOS, and XCode can handle simple git features for you.
I'm currently migrating my project to Swift3 as I know that there is one bug I have under iOS 10 that needs to be fixed.
So I installed iOS 10 on one of my devices.
Now I can't run my app on the device, getting the 'Could not find developer disk image' error.
So I downloaded the latest Xcode8-beta.
Now my code can't be compiled - I first have to convert it to the newest syntax.
So while fixing all the non auto-converted syntax issues, I'm getting errors for frameworks I'm importing, too:
"Module file was created by an older version of the compiler"
Which - to my understanding - means that this framework needs to be recompiled with the current version of XCode.
This would mean that I would have to cross my fingers that all the frameworks I use are up-to-date, or otherwise, fix those, too?
Is it not possible at all to use 'deprecated' frameworks?
Is this Apple being super strict to get rid of any Swift1/2 code as possible?
This would mean that I would have to cross my fingers that all the frameworks I use are up-to-date, or otherwise, fix those, too?
Is it not possible at all to use 'deprecated' frameworks?
Is this Apple being super strict to get rid of any Swift1/2 code as possible?
Yup. Swift 3 is it.
I feel bad for those that had to convert their C code to swift 2, and now swift 3 is coming xD
Hopefully they will make the transition easier with the final release version, and that shortly after that all of the major frameworks will have been updated (for you to recompile).
You need to recompile the frameworks. Even frameworks managed with dependency managers like Carthage (which recompile on each update command) are still having problems with XCode 8 Betas / Swift 3: https://github.com/Carthage/Carthage/issues/1440
http://thenextweb.com/apple/2016/05/09/swift-3-0-developer-previews-wwdc/#gref
Does this mean anything? Will I have to completely rebuild my apps or merely convert 2.2 syntax to 3.0?
Swift 3.0 will not be compatible with 2.2. Here is the list of the current proposals, it also details what has been implemented already, and what will be :
https://github.com/apple/swift-evolution
You will not have to entirely rebuild your App, but you will have to adapt your code.
I'd say no. Every Swift app comes with its own runtime and standard libraries of whatever Xcode version you used to build it. Some of my Swift 1.0 app still runs on the latest version of El Capitan.
Source incompatibility means you can't take valid code written in Swift 2, feed it to the Swift 3 compiler and expect everything to go smoothly. There will be errors and deprecation warnings, much of which you already see today with Swift 2.3.
You also can't take a compiled application written in Swift 2 and make it run without modification on a Swift 3 runtime either. Swift is lacking a stable Application Binary Interface (ABI) at the moment. That's why every Swift app must carry its own runtime. OS X and iOS don't provide those at the system level. Hence Swift app tends be larger in size, more of a problem on iOS than OS X.
With Swift 3, Apple is trying to establish a stable ABI so your compiled Swift 3 can run without modification on the Swift 4 runtime, whenever that comes.
What about source code compatibility? No one knows what Chris Lattner has in mind or what he considers archaic. Removing the ++ and -- operator in Swift 3 seem superfluous to me. And why kill C-style for loop too?
I'm currently adapting all my code to the present state of Swift 3. The existing code is certainly not compatible; most methods have been renamed, case names have been lowercased, and so on. To what extent Apple will assist by providing a migration tool is unknown, as that's in the future.
#CodeDifferent provided a great answer, but I'd like to extend on it.
AFAIK, if your Swift 2 app is compiled with its own runtime linked in (i.e., not relying on the system runtime), then your app will run fine & there's no need to rebuild on a Swift 3 machine to run on a Swift 3 machine. But if there's no runtime compiled into the app, then your app won't run on a machine with a Swift 3 ABI.
Of course, if you are going to compile with application with Swift 3, then you will have to re-build.