With Tomasz I added a new Swift spike to the iOS board:

Basically it's a dry run to convert some of the most simple code in the app codebase to Swift to see what issues we encounter and give us a rough baseline for how quickly existing code can be converted.

The spike should not be considered to signify the moment we officially fork the code (with the pre-Swift base being maintained only for iOS 6 bug fixes). Timing for this forking should be informed by what we learn during the spike and Dan will make the call as to when we fork.

When we do fork and enable Swift for ongoing development, I do not think we should necessarily immediately switch all development to Swift. My preference would be to switch completely to Swift over the course of a few months as we gain experience and mastery of it. We may find this doesn't actually take months, and I suspect it won't, but I would prefer to ease into it.

Does this sound ok?

On Thu, Nov 13, 2014 at 1:45 PM, Dan Garry <dgarry@wikimedia.org> wrote:
The product expectations here are:
  • After the transition, no new features will be backported to Objective C to be used on iOS 6. All new features will be developed in Swift. The exact feature cut-off is to be defined by product and design (setting up a meeting about this tomorrow).
  • Crash fixes and major bug fixes will continue to be handled on the iOS 6 version for the mid future (e.g. next few months).
  • Code will be refactored from Objective C to Swift as time allows, e.g. possibly as an onboarding task for new engineers. There will be no planned effort in the short- or mid-term (e.g. next few months) to refactor old code from Objective C to Swift, although this is the plan in the long term.
Let me know if you need more, or need any clarification.


On 13 November 2014 13:35, Tomasz Finc <tfinc@wikimedia.org> wrote:
Thanks for kicking this off Dan. I've been following Swifts
development from the sidelines and I'm eager to put it through its
paces. Given that modern iOS releases can support hybrid Swift and iOS
apps, the risk of experimenting is low and potential pay off is high.

Addressing some of the questions I've gotten.

= Existing Engineers =

I expect all of our engineers to be well rounded and exposed to
multiple languages. This means picking up new languages as necessary
for their job and anticipating future platform changes that require
new expertise. Swift is just another one of these.

While jumping between some languages can be a huge leap, Swift is not.
The language [1], migration [2], and iOS/OSX integration are well
documented giving me confidence that we have the resources to move
forward giving our current resourcing.

= Team Growth =

I expect no significant change to recruitment in the short term 6month
- 1year. I expect a significant difference in the 1yr - 2yr range as
more people come up to speed and have built real world applications
with it. Thus I anticipate and huge help in hiring in the future with
this change.

I do expect more volunteers experimenting with our code base if its
swift based and I know that we have internal non app staff who are
curious to join these efforts. I can easily see a 1day hackathon
centered on helping us get to swift pulling in various resources.

Next step will be to define a spike to assess a migration. [3]

Dan, i'll need you to define what this migration means to product if
we decide to go forward. Product needs to define what features will be
frozen, what if anything need to be backported, and which iO6 bugs we
will respond to.


[1] - https://developer.apple.com/library/ios/documentation/swift/conceptual/Swift_Programming_Language/TheBasics.html
[2] - https://developer.apple.com/library/ios/documentation/swift/conceptual/buildingcocoaapps/Migration.html
[3] - https://trello.com/c/dgYqIuId/21-spike-hr-determine-whether-we-re-ready-to-migrate-to-swift

On Wed, Nov 12, 2014 at 10:05 PM, Dan Garry <dgarry@wikimedia.org> wrote:
> tl;dr: The programming language used to develop new features by our iOS app
> engineering team is changing from Objective C to Swift at some point in the
> near future.
> When making a native app, the language you have to implement the app in is
> chosen by the third party responsible for the platform. For iOS apps, Apple
> chose Objective C to be the language the app is written in. Objective C is
> a... very strange language. It has a lot of quirks that slow down
> development.
> To solve the above problem, you can now write apps in a new language called
> Swift. Notably, Swift has features that make it less error prone and more
> concise than Objective C, which should increase our velocity of feature
> development. Swift is also much more readable and in-line with other
> languages, which lowers the barrier of entry (which is currently very high
> with Objective C).
> Importantly, Objective C and Swift can live alongside each other. So, when
> we "switch to Swift" we do not need to rewrite all of our existing code from
> Objective C to Swift. Instead, we can just start developing new features
> using Swift, and slowly rewrite the old code from Objective C into Swift as
> time allows.
> On the downsides, Swift is only supported on iOS 7 and above. iOS 6 only
> represents around 5% of our user base, and we can pin iOS 6 users to the
> last version of the app we released before we used Swift. We need to decide
> what the last set of features we're want in that build are before we switch.
> Here are our next steps:
> Evaluate more concretely whether Swift actually fits our needs or not.
> [Engineering]
> Decide last set of features for our iOS 6 build. [Product/Design]
> Thanks,
> Dan
> --
> Dan Garry
> Associate Product Manager, Mobile Apps
> Wikimedia Foundation
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Dan Garry
Associate Product Manager, Mobile Apps
Wikimedia Foundation

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