I am building a new framework. The project is to be coded into Swift language, however the clients using this framework have the freedom of using either swift or Objective-C framework.
The question is how do I start. There could be numerous issues like
using structs in swift code but it cannot be made available in
objective C framework.
optionals are missing objective c
Even if I
write different set of files for Swift and Objective C, how will I
map them onto different frameworks under the same project.
Enums with other than Int as rawValue can't be used.
Tuples would not work
I know there have been a few questions around this but none have any satisfactory answer.
PS - Any link to a tutorial or blog would be super helpful too
I did this and got some unexpected results: I have trouble integrating the framework in Swift application. Objective-C works just fine.
You mentioned some of the caveats here.
I suggest doing this iteratively while writing test application in Objective-C which uses all the features. This way if there is some feature that does not cross Swift to Objective-C boundary well, it will be discovered as early as possible.
Your remarks about issues are generally correct with one small exception: optionals are not missing from Objective-C, they appear as nullable/nonnull modifiers on variables and method parameters. Although this does not replace optionals fully, it helps detecting issues early in the process.
Here is a random list of some other issues I discovered:
Bridging between Swift Error and NSError used in Objective-C. The conversion is not always as smooth at it could be, so better use NSError in exported code.
If you mix Objective-C and Swift in your framework, you cannot use bridging header, instead using modulemap files which tend to turn pretty large and complex.
Since you cannot embed frameworks inside a framework, you have to make sure that the application sets ALWAYS_EMBED_SWIFT_STANDARD_LIBRARIES flag for its target. This has to be clearly indicated in the documentation. Also, when creating fat library for your framework, you have to strip these files from the distributed SDK.
And, as I said in the beginning, I still have no success using the resulting mixed language framework in Swift application.
Hope, this will add to your list of things to take into account when developing the library.
Related
I've been the last week trying to serialise all of the classes of one iOS project (Objective-C).
Due to I use to do it in Android projects with Avro (Apache) library, I've been trying to do the same in the iOS project, however, the first thing that I noticed is that there is not too much information about Avro in iOS.
First thing I tried:
Implement the library ObjectiveAvro using CocoaPods but some classes in the library Avro C were not found when imported.
Second thing I tried:
Remove and do again the previous process but this time only with the Avro C library but the same error appeared.
Third thing I tried:
Implement BlueSteel framework using Carthage. This is a swift library but I wanted to try if I could use it somehow in an Objective-C project. I couldn't.
I just need to serialise and deserialise data providing a schema as you can do with Avro (Android) in an Objective-C project and the last thing that I want to do is convert the whole project to Swift.
So do you know what's the current way to do that in Objective-C?
I could figure it out how to do the Third thing I tried:
Basically, it's necessary to import the library through Carthage, then create a new Swift class which is the one that is going to "talk" with the Swift library, due to we are in an Objective-C project. XCode will ask you to add a "header-class" and press "yes".
Then it's as simple as using the Swift to call the library methods and call the Swift class from the current classes. Swift class in Objective-C project
Finally just to inform that the BlueSteel framework is a nightmare due to is really limited and really poor documented therefore I still don't know a real alternative.
However, if you're going to use it, have in mind that the classes are not autogenerated so you need to do manually the conversion to Avro and sign results.
I want to import a Swift framework called "Beethoven" into Objective-C project. I import this framework via cocoapods.
The problem is that framework is written in pure swift. Since the classes are not subclass of NSObject they can't be used directly in my objC classes.
I am newbie in Swift and intermediate in objC, but I think there may be 2 solutions for that:
1-Modifying the whole library: which is probably not an optimal solution.
2-Using a new class which behaves as an interface between swift framework and my objC code. I think second solution will be a better alternative in terms of time and effort needed.
Actually below given post explains modifying the pure swift classes but I don't know how to apply this in my case.
How to use Swift non-NSObject subclass in Objective-C
As I mentioned I am not a very capable programmer and there may be better solutions for that problem. I would be grateful if someone can help me and suggest the best solution for integrating pure Swift framework into my objC project.
NSObject is usually not the only problem. Swift has many features that are not supported by Objective-C. To name a few: swift value types (struct's), swift enums with attached values. If a library uses any of those, it will not be possible to auto-generate an Objective-C header (.h) for it.
Adapting the code of the library on the spot might work, but it is likely more work long term in case if you ever need to update that library again.
Your 2nd approach sounds better: create a layer that is compatible with Objective-C on top of the library which exports methods that need to be exported with #objc and adapts the types. If you go that way consider making a PR contribution to the original library so that everyone could use it in Objective-C projects, and you share responsibility of updating it when the swift code changes.
The 3rd approach would be actually to rewrite some parts of you app to Swift. That might or might not be easier depending on the size of the part of the app that is using the library and how well it is isolated from the rest of the app.
I've got an iOS dynamic framework written in Swift and would like to know what ways I can "export" the framework for use in external projects, while leaving the implementation unexposed.
The "best" solution I've come across so far is from this article, but for some reason autocompletion stops working when I'm trying to use classes from the framework in a project.
Right now I'm using a Xcode workspace to use the framework within a project. However, as mentioned I don't want to have the implementation exposed.
I understand that Swift doesn't have separate interface and implementation files found in Objective-C, but am just curious as to how other people approach this.
Can we create iOS app with swift and obj c both.My half app is made using OBJ-C and just want to improve apps performance so is that possible to use swift in between
Yes you can.
You have to add objc header #imports in the <module name>-Bridging-Header.h that you want to make available in swift, and you can use swift code from objc by importing the <module name>-Swift.h file in your objc code.
Note that the latter header file is automatically generated when building, and it is not visible in the project navigator - but you can open it by cmd+click-ing its name in an existing #import. Also to note that if compilation fails, most likely the file will not be generated.
Last, I highly recommend that you avoid circular references between objc and swift - for instance, creating a SwiftClass, inherited from BaseObjcClass, and using SwiftClass from objc - I've experienced that it doesn't work (compilation errors), and I am not aware of any workaround
Yes, you can. You just need to follow this:
https://developer.apple.com/library/ios/documentation/Swift/Conceptual/BuildingCocoaApps/MixandMatch.html
Apple’s intention to replace the Objective-C language using Swift, it is not practical in the short term simply due to the fact that developers are deeply entrenched in Objective-C. Rather than force Swift down the developer’s throat, Apple has made it easy to allow Objective-C to interoperate with Swift.
http://mobiforge.com/design-development/using-objective-c-and-swift-together-ios-apps
Dec 2018 - I found this useful YouTube video that helps explain what files you need to add and how to make the connections.
YouTube - How to use Swift and Objective-C in the same project
To provide cross compatibility, Swift allows for the generation of a bridging header so that Objective-C can communicate with Swift classes.
Due to Swift's wonderful namespacing we no longer need to worry about prefixing our Swift files as they are namespaced by their containing framework. A UIView for instance is implicitly namespaces as UIKit.UIView.
Now that Apple are pushing frameworks, I was wondering what the best practices are to avoid header collision when there exists two swift bridging headers with the same symbols.
An example: Say we have two frameworks that have declared a Swift class called Downloader. The Downloader provides the interface: downloadWithURL(url: NSURL)
Generating a bridging header will yield a Downloader-Swift.h file for both of these frameworks. Thus causing a collision. What are the best practices to avoid this?
According to Apple's engineers the <#Module Name#>-Swift.h header uses a macro that mangles the name so as to avoid conflicts (see WWDC video Swift Interoperability In Depth, beginning at 45 min, 40 sec). They gave an example of a Document Swift class:
SWIFT_CLASS("_TtC5MyApp10Document")
#interface Document : UIDocument
// rest of the interface...
To your Swift code, the class will be available as MyApp.Document, if MyApp is the module it is in. So, if you have two Swift classes of the same name coming from different modules – say, one is your own and the other from an open source Swift framework SomeFramework – they will be available to your Swift code as MyApp.Document and SomeFramework.Document...
On the Obj-C side, however, importing these two classes into the same lexical scope leads to Duplicate interface definition for class 'Document' compiler error. That's just Obj-C... In the vast majority of cases, though, this will not be an issue since you can still import these two classes across the app as long as they do not trespass each other's territory. Indeed, how often would you want to use MyApp.Document and SomeFramework.Document in the same module of your app? As we are moving into swifter times, I'm not sure this particular issue warrants a particular strategy, compared to so many urgent issues, such as, multicore, distributed, functional, haptic, anticipative, wearable, autonomous, etc...