[aerogear-dev] Parallel support for a Cocoapods Swift/Obj-c library

Corinne Krych corinnekrych at gmail.com
Thu Jan 22 12:35:41 EST 2015 

Oki for b, make sense and is easy to understand.

We go for 2 podspecs on 2 different branches. 
In aerogear-io-push on 1.x_dev brnach we keep podspec unchanged.
on master branch (Swift version) podspec get renamed to AeroGear-Push-Swift

On side note, interesting use case of QueryKit Swift-first lib, bridging from Swift to obj-c. How you turn strongly typed designed library to dynamic lg. Generics -> AnyObject like shown in [1]
it could be the case for ex if you want ot use ou jsonsz lib in obj-c but i’d simply go: use obj-c  fwk like mantle...

++
Corinne
[1] https://github.com/QueryKit/QueryKit/blob/master/QueryKit%2FObjectiveC%2FQKAttribute.swift#L10

> On 22 Jan 2015, at 15:40, Christos Vasilakis <cvasilak at gmail.com> wrote:
> 
>> 
>> On Jan 22, 2015, at 4:21 PM, Matthias Wessendorf <matzew at apache.org> wrote:
>> 
>> Wow, thanks for all the details around here
>> 
>> On Thu, Jan 22, 2015 at 2:01 PM, Christos Vasilakis <cvasilak at gmail.com> wrote:
>> Hi team,
>> 
>> a little heads up on an issue that I‘ve been looking the last days, on how to proper support both an Obj-C and a Swift library (in-parallel) on Cocoapods. There was a discussion on the cocoapods issues tracker[1] basically around two ideas:
>> 
>> a) being a separate project, with a new name plus utilising Swift specific language propers.
>> b) having one project, utilising cocoapods subspec mechanism to include specific files per spec requested. In a nutshell users will employ in their Podfile something of a form:
>> 
>> —
>> pod “MyFooBarLibrary/Objc’    (objective-c) 
>> or
>> pod “ MyFooBarLibrary/Swift’   (Swift)
>> —
>> 
>> Solution (b) was intrigued and went on to discover more, since I haven’t used before the subspec mechanism and was a good opportunity to learn. The issue mentioned two projects, QueryKit[2] and ReactiveCocoa[3] (their Swift branch) that utilise this mechanism, so I dive in trying to see how it works. 
>> 
>> My realisations:
>> a) both projects are designed with ‘Swift first’ approach, employing _some_ 'Objective-C code’  to ease the interaction in a mixed project e.g Objective-C code calling the ‘Swift’ library, see [4] where the author describes more details on this.
>> b) since ‘Swift first’, both produce frameworks where they can be integrated either in objective-c or swift language projects, no ‘static-library’ targets.
>> c) both are designed for iOS >= 8.0
>> 
>> ouch - what do they do for iOS7 ? 
> 
> no support for iOS 7, QueryKit and ReactiveCocoa(swift branch) are fairly new and designed to work on iOS 8 and later
> 
> Note: ReactiveCocoa has a ‘master' branch with support of iOS 7/8 but ‘objective-c’ only.
> 
> 
>> 
>>  
>> 
>> To make it short and from my understanding,  the projects are _not_ designed around the idea of: take either the Objective-C or the Swift port in you project, but instead employ an Objective-C subspec to “ease” the interaction in a mixed environment, aka Objective-C code calling the Swift library.
>> 
>> Regardless and to better understand, I did some testing with our push-sdk:
>> 
>> a) having a single Swift Project employing both the objective-c code and Swift code
>> b) having a .workspace with a) Obj-c xcodeproj, b) Swift xcodeproj.
>> 
>> In both cases, this mixed approaches, at the end caused issues and wasn’t able to generate a proper solution. Issues around a) cocoapods 'pod install’ steps, b) tests on the library are done with two different dependencies c) various other integration issues…
>> 
>> It’s my sense, the most clean way is to go with separate libraries, that is solution (a) described above (a solution proposed also from @orta [5]) This has the added benefit of cleaner 'logistics’ that is: commit history, releases, static/framework library generations etc etc.
>> 
>> +1000 :-) When reading, I was actually wondering about these logistics :)
>>  
>> 
>> But there is one issue if we go with separate approach:  _cocoapods naming_, that is how to properly separate between the two.
>> 
>> Currently searching for AeroGear-Push in cocoapods.org site we get the following:
>> 
>> <Screenshot 2015-01-22 13.56.36.png>
>> 
>> 
>> In my cocoapods PR [6] I went with the approach to name the ‘Swift’ equivalent library as 'AeroGear-Push-Swift’, so the same searching above will reveal:
>> 
>> —
>> AeroGear-Push
>> AeroGear-Push-Swift
>> —
>> 
>> Some of you have already noticed, that the ‘hyphen’ character as a podspec name doesn’t work well with a Swift Project, cause the podspec name is used as the name of the final #import statement the user does. That is the following import statement doesn’t work:
>> 
>> —
>> import AeroGear-Push-Swift
>> —
>> 
>> Solving this, there are two approaches:
>> 
>> a) rename both library podspecs : Objective-C to -> AeroGearPush and Swift to -> AeroGearPushSwift
>> b) continue the same naming, but use the new ‘module_name’  podspec directive in the Swift project(added in cocoapods [6]) to specify the final module name the user will use on the import. That is the approach I have taken in my PR[6]
>> 
>> +1 on b), using the module_name - nice addon to CocoaPods
>> 
>>  
>> 
>> If we go with (b) the entries will look like this:
>> 
>> ——
>> Obj-c:  (no changes needed)
>> 
>> Podfile: pod 'AeroGear-Push’
>> 
>> Class:   #import <AeroGearPush/AeroGearPush.h>
>> 
>> 
>> Swift:
>> 
>> Podfile:  pod 'AeroGear-Push-Swift’
>> 
>> Class:    import “AeroGearPush”  (notice _no_ ‘Swift’ postfix is needed cause of the ‘module_name’ override)
>> 
>> ——
>> 
>> I am fine with both albeit more towards (b) mostly not to break existing ‘pod installs’ the users may use and since support with the ‘module_name’ directive is provided from cocoapods.  Current PR[6] goes with this approach.
>> 
>> Let me know your comments and suggestions
>> 
>> Thanks
>> Christos
>> 
>> [1] https://github.com/CocoaPods/CocoaPods/issues/3016
>> [2] https://github.com/QueryKit/QueryKit
>> [3] https://github.com/ReactiveCocoa/ReactiveCocoa/tree/swift-development
>> [4] https://github.com/CocoaPods/CocoaPods/issues/3016#issuecomment-69092100
>> [5] https://github.com/CocoaPods/CocoaPods/issues/3016#issuecomment-69073109
>> [6] https://github.com/aerogear/aerogear-ios-push/pull/41
>> [7] http://blog.cocoapods.org/Pod-Authors-Guide-to-CocoaPods-Frameworks/
>> 
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>> 
>> 
>> -- 
>> Matthias Wessendorf 
>> 
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