I work with an App that's 100% Objective-C and I'd like to start transitioning over to include Swift. Due to the size of the codebase, it's unrealistic that I'll have a 100% Swift app anytime soon.
As soon as a swift file is added, I noticed that the app size increases because now, the app needs to the include Swift run-time.
How else does things change? As soon as you include a Swift file, what is the process that the compiler and linker undergoes to ship a binary that is now multiple language & related frameworks?
Are there any other caveats in transitioning into a mixed language world in a somewhat large codebase?
In my experience, it works surprisingly well. It is advisable however, to wait to Xcode 7 / Swift 2.0 / Objective-C with generics support as that will eliminate a round of updates, allow you to interop from Objective-C with more elegant Swift code, and eliminate the Swift RT linking concern now that they have stabilized the runtime.
Aside from that, both compilers need to run, Swift first, Objective-C second, the swiftc compiler can be pretty fast or really really slow, depending on what innocent and otherwise legal Swift code that you write (this is also true of a Swift-only app of course).
Getting started, you need to read the interop guide, learn how the bridging header works, and are then mostly on your way. I would say that having a mixed app is actually a blessing as you are not pressed to learn and do everything at once. Opinions will vary of course, but this is mine.
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I'm looking to make an app which allows you to use Swift code within the app - similar to other Swift-based learning education apps to help you learn the language.
Is there a way to use the open source Swift code, for example, in any way to understand the syntax and possibly run the code for typed-in Swift code?
An example of an app I found on the App Store which can do this is called Sedona.
From GitHub apple/swift/.../Syntax there looks to be Swift syntax APIs, presumably for use by IDEs.
Am I looking in the wrong place?
Do these types of apps make their own Swift translator?
Is there some other way this is done?
Efficiency & optimization is not a priority, however would be a benefit.
It in no way needs to include very complex Swift.
Note: This is for an iOS app only, so Terminal commands would not work.
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.
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Previously with objective-c code, I could "Analyze" - CMD + Shift + B and Xcode would warn me of all kinds of wrongdoings on my part.
It seems that with Swift, I can do no wrong! No warnings of any kind! But clearly there is a memory leak in my code.
Is there some setting I have to enable to get Swift to analyze my code properly? (I am aware I should use the profiler and test on an actual device, which I do, but I wonder why "Analyze" doesn't do anything.
Unfortunately no. Even many releases later, the latest version of XCode (6.4) still cannot do Swift analysis. The 'Analyze' option only works for the Objective C files in your project.
Let's hope the next version will have it, along with the refactoring capabilities which also are still limited to Objective C code.
To this moment (Xcode 8.3.x) Static Code analysis skips Swift code. Some Swift warnings cover some of the issues previously detected by the analyzer.
Also the upcoming Xcode 9 (presented in WWDC 2017) does not announce any change in this direction.
Many issues detected by the static Analyzer of Obj-C are for the most part prevented by the actual Swift language (e.g. unintended fall-through in switch statements). Other issues and scenarios formerly caught by the analyser, are now caught directly by the Swift compiler.
Many flows and scenarios leading to program crash - (e.g. accessing null pointers, leaving dangling pointers, or accessing released memory blocks) are hardly possible in Swift. Swift strong typing, heavy use of optionals, the requirement to completely cover protocols, and switch-case over enums, etc. remove another bunch of issues previously found by the analyzer.
A Swift static code analyzer will need to go to another level in analyzing program logic, which is much harder, and theoretically impossible to do completely.
So - although I'm quite thrilled to think of some future Xcode Analyzer, I wouldn't hold my breath waiting for it
Update:
As more and more people are down voting my post, just small update from my side. It seems that indeed apple just did allow for pressing option "Analyze" but in the background it does nothing (state for 2016.04.21, though I am not working on iOS for the moment and probably I don't have the latest version of Xcode).
below my original post:
Just for next readers of this article. At this moment Xcode 7 is already able to analyze also Swift projects. Refactoring is still not working though.
BR,
Darek
I need to present and open pdf documents in my app. I would like to avoid third part libraries, because of update reasons (and I couldn´t find anyone created in swift).
I have been looking at QLPreviewController, UIDocumentInteractionController and presenting the pdf in an UIWebView. All these alternatives works fine for just presenting the pdf but I can´t find any built in search. I want functionality like the iBooks app.
Any advice is appreciated!
You'll likely wont find any 3rd-party frameworks written in Swift yet, simply because as of Swift 2.2 it's not binary compatible yet, and any binary framework written in Swift would be very fragile to break with even a minor update of Xcode (and updates to the compiler, that is).
I'm working on the commercial available PSPDFKit SDK for both iOS and Android. We're actually using a lot of C++ internally since raw performance is very important and Objective-C (and for many things, also Swift) are not yet fast enough for certain tasks.
We did invest a lot of time in adopting the latest Objective-C features such as nullability and generics next to declarations such as noescape for block-based API to make our SDK great to consume from within Swift.
While a separate Swift-wrapper could offer additional convenience, you'll find it very simple to use, and we're always working to adopt more features that improve bridging as they come available - there are a few interesting things in the Swift 3 proposals.
If you do not want to go the framework route, you can use CGPDFScanner to base a custom text extraction engine on. You will need to read up on Character Map Parsing - Page 446ff and many other sections - extracting text from a PDF document is surprisingly difficult, and after much work you'll be left with individual glyph positions and need to approximate where words are and if the document uses spaces or if you need to synthesize your own to correctly extract text. It's something that just takes a lot of experimentation and approximation to get right.
I'm working on a project that draws functions on a plane (Similar to Apple's Grapher utility).
I'have already compiled this app few months ago in Obj-C, and was running clean and fast.
With Swift, I changed a bit the scheme of the app, but I'm still using CGMathParser, a great collection of classes to manipulate and evaluate strings like y=sin(x) or y=log(tan(x))
However the app is now slow and laggy, and I'm thinking that the reason hides in the fact that I'm mixing Swift with Obj-C.
Do you know if there is any kind of parser already optimized for Swift that will be fast enough?
The Swift compiler enforces bounds checks and various other 'safety' features. If you compile with the -Ofast option these checks are removed, which typically makes your app run a lot faster.