I'm relatively new to Swift (I've tinkered with Python and HTML in the past)- but I'm currently working on an app with a group.
This app already exists as a desktop program written in Ada and we were hoping to port it over to Swift and put out an iPhone app.
My understanding is that I can (likely?) turn the Ada into C with a converter, then reference the C in Swift? Is this correct, or have I overlooked something due to not being familiar with the languages?
If correct, how would I go about actually executing this since I have little experience in Swift and C?
This is a pretty loaded question, so thank you for any help or insight!
edit: said desktop application is open source and available for all use- I do not intend on stealing anyone's work
I'm assuming that you can easily pull out the parts of the Ada program that you want to use in the iPhone program. If the code that you want to port over has other dependencies, then you have to make sure that you can get all of these dependencies for iOS as well. This may be extremely difficult for UI toolkits, if you use one.
To call foreign functions in Swift, you usually need to use a bridging header. Your target's bridging header contains C and Objective-C declarations of classes, functions and variables that Swift should be able to call into. As long as the language that you want to call into can export C-compatible bindings (which should be the case of Ada), then you will be able to call these bindings by declaring them in your bridging header.
If the part of the desktop Ada program that you want to use can easily be isolated in a library (static or dynamic), and you are capable of building that library as an ARM Mach-O library, then it's simply a matter of declaring the functions that you want to use from the library in your app's bridging header. You can refer to GNAT User's Guide for Native Platforms: Interfacing to C for the directives to use to expose an Ada function to C, and by exposing it to C, you're also exposing it to Swift. I'd try this first, as maintaining the almost-unmodified Ada source is almost certainly going to be easier than maintaining a mechanically-translated C version of the Ada source.
If that doesn't work, then yes, translating the Ada source to C code will also allow you to reference it from Swift. You will also have to ensure that the functions that you need to call are declared in your bridging header.
It looks like it used to be possible to compile Ada in Xcode when Xcode still supported the GCC compiler. That was removed a while ago.
If there are translators that will translate Ada to C then you could use C natively in an Objective-C iOS app. (Objective-C is a pure superset of C, meaning that all C code is also legal objective-C.)
Swift "plays nice" with C and Objective-C as long as you limit yourself to the types and classes that C and Objective-C understand, but inter-operating between Swift and C/Objective-C is somewhat tricky and tedious. You would have a fair amount of reading and study to do in order to learn how to build an app that uses both, on top of everything else you would need to learn.
Unless you're dealing with many thousands of lines of Ada code it might be better to find somebody who knows both Ada and Swift to translate the code for you, or for you to learn Swift and then translate it yourself.
Unfortunately, There is, at this time, no Ada compiler which targets iOS available to the public.
If you have cash to spend you could contact AdaCore for one, don’t expect it to be cheap though.
Believe me, there are some of us who would like to target iOS with Ada.
I am only aware of two Ada to C compilers, the most powerful one (AdaMagic) is now known as MapuSoft Ada-to-C/C++ changer. You'll need either Windows or Linux execution environment to run translator (Wine, Docker, etc. on macOS). Also, you'll need to limit yourself to Ada 95. AdaMagic is said to support a "subset of Ada 2005", but I am yet to stumble upon this subset. Also you'll need to port the runtime or a part of it. If you disable runtime checks, the amount of runtime required to port becomes lower, so it is up to you how much time you are willing to spend on it.
It has two modes of operation, either targeting C, or C++, I recommend C++ because throw-catch is a better match with modern Objective-C runtime (utilizing C++ ABI behind the scenes) than C setjmp/longjmp.
With some effort you'll get something up and running.
It is a pity Ada developers are so unaware of this option. Maybe somebody could find time to port AdaMagic to EmScripten, iOS, Elbrus or whatever essential target the humanity is missing to start mass Ada adoption.
Others advised producing Swift bindings from bridging headers, but IMO the winning strategy would be to write glue code in Objective-C++ hybrid. Objective-C++ will have access to both Swift code (viewed as external Objective-C classes) and Ada-to-C++ translated code. For instance, it will be able to catch C++ exceptions from Ada and throw Objective-C ones or vice versa.
Another compiler is GNAT CCG aka SPARK2C. It is designed to target embedded devices having no other Ada compiler. It supports recent Ada standards, but is very limited with regards to features requiring runtime. Basicly, there is no runtime. No runtime, no problem. Nothing to port. In this compiler one can return limited record from function (Ada 2005+ feature), but cannot have RAII, tasking, etc. I guess, that are far more strict requirements than Ada 95. GNAT CCG is not yet publicly available, but I expect it to appear before annual Make with Ada, otherwise that would be a very stupid situation.
Another options are Ada-to-Java or Ada-to-.NET, maybe they can work for your application better than others.
As an experienced Objective-C developer who is now learning Swift , I'm really missing some of the reflection and dynamic features of Objective-C.
For eg: I had written a JSON serializer which automatically mapped keys and values using KVO and Objective C introspection , and there are open source libraries like Mantle which do this.
I could declare my object as an NSObject subclass and proceed but I feel that this is not the Swift way of doing things.
Is there any other way to accomplish the same tasks , while avoiding boilerplate , using what Swift provides ?
EDIT: (2016) this answer is auto-dated. Some of the advice may still be relevant but now that Swift is open-source, I would look into other possible answers.
There is no native KVO reflection like what you described built into Swift. See:
https://stackoverflow.com/a/24092370/798682
And based on what we do know about how the Swift compiler optimizes method execution at compile time (vs the pure runtime implementation of ObjC) it doesn’t seem likely to be added anytime soon. See https://stackoverflow.com/a/25438299/798682 and
http://blog.untitledkingdom.co.uk/obj-c-vs-swift/
for more info on that.
With all that being said, here is a blog post on some KVO alternatives in Swift:
http://blog.scottlogic.com/2015/02/11/swift-kvo-alternatives.html
and another that details some of the reflection capabilities that are in Swift:
http://freecake.angelodipaolo.org/simple-reflection-in-swift/.
I'm trying to translate an Objective-C app into Swift and I don't know how to implement a malloc.
Is it possible to use it in Swift?
Thank you
You need to implement a bridging header when you use ObjC or C from Swift. The functions exported by your bridging header are then available in your Swift app/module. See here, for the overview.
If you just need to "call some code" on the C-side, then the functions exported from C are basically just wrappers for Swift. However, if you need to interact with the data returned from those functions -- especially if malloc'd and not a simple primitive -- Swift has a number of C related types ready for your use (see here for specifics).
Furthermore, if you're trying to wrap or interact with C++ code, you can't directly do so from Swift. You have to setup an initial interface with ObjC or C for the C++ code, and then bridge that to Swift. Not really fun at all, but thankfully it's not as common a use case as bridging ObjC (primarily) or C.
... and for what it's worth, unless you need low level Core Audio for some reason (granted, like porting an app you already have), AVAudioEngine (iOS8+) is so much simpler for any applicable use case than Core Audio, and is readily available in Swift.
I see a lot of code for swift ios tutorials on the internet still using the old objective-c data types like NSDictionary and NSArrays instead of using the modern Array and Dictionary data types that come with Swift.
Most often I see a lot of type casting going on using as? etc. I have seen this mostly in examples involving json parsing from a webservice.
So why is this? Is this because swift isn't fully compatible withe cocoa touch apis yet? Or is there another reason like performance?
Even though you used the NSArray and NSDictionary, swift will automatically bridges to their native swift equivalent Array and Dictionary.
By using the Swift native, the performance will be great.
Please refer the documentation
Because you are calling code in the Cocoa library that uses NSDictionary and NSArray and Apple isn't going to rewrite all these libraries.
Your question whether Swift is not fully compatible with Cocoa APIs is nonsensical. It is compatible, or you couldn't call Cocoa. But the Cocoa APIs are not changing. Cocoa is a library; it uses and supports the classes that it uses and supports, and using a different programming language isn't going to change that.
Do I need to learn and convert my entire codebase to the new Swift language if I want to support ios 8?
No. The APIs available from Swift are exactly the same as the APIs available from Objective-C; you can code against any iOS 8 APIs from either language.
To start writing in Swift, there's an option called Migration. It will convert your existing code into swift code
Migration provides an opportunity to revisit an existing Objective-C
app and improve its architecture, logic, and performance by replacing
pieces of it in Swift. For a straightforward, incremental migration of
an app, you’ll be using the tools learned earlier—mix and match plus
interoperability. Mix-and-match functionality makes it easy to choose
which features and functionality to implement in Swift, and which to
leave in Objective-C.
NO.
Your Swift code can be run alongside your Objective-C code because Swift is built with the same compiler, ARC management and runtime as Objective-C.