Incremental Swift
We said, “Instead of living with just Objective-C or Swift, let’s be a two-language code base. Let’s commit to that.” And this was actually a smart decision, I think, because realistically if we were porting our app one piece at a time, it would take us years to get completely to Swift anyways.
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Xcode forgets what language you are looking at and gives you the header for the wrong one. More importantly, developers need to know two languages, which is also a disadvantage in terms of education. And finally we have to deal with all of those messy interoperability features i.e. bridging headers and auto-generated Objective-C.
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The solution we landed on was to annotate files while you import them. Your Swift bridging header is the firewall between your Swift code and your Objective-C, as long as you annotate things there, you will be safe.
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All we decided is that if you are going to use, for example, a generic or struct, make sure it is flagged as private. You can write your very Swifty code, but it will be interfaced for it. You are forced to write something that you can still use from Objective-C.
