To use API v2 in iOS platform, we need an objective-C version

@Steve, thanks for providing the additional information and for your transparency. I'll just quickly reiterate that for us (and for many other iOS developers), including any Swift code in our app is not an option at this point in time.

Your decision to not write the SDK itself in Objective-C on the grounds that "the experience of using an Objective-C library from Swift is not great" doesn't seem logical to me, because the converse (not being able to use Swift code in Objective-C) is a far more severe problem. Also keep in mind that all of Apple's iOS system frameworks are written in Objective-C, and Swift developers are more than capable of using them. Apple has made some great additions to Objective-C recently (nullability, generics) specifically to improve this type of interoperability.

If I were in your shoes, I would invest your time into re-working the new SDK to be written solely in Objective-C, and perhaps distribute a nice Swift wrapper with fancy enums if that is something that developers are interested in. Maintaining 2 separate SDKs does not seem like a good choice. The majority of iOS apps today are written in Objective-C, not Swift. Your goal as an SDK vendor should be to ensure that your SDK is usable by the most number of developers, and potentially excluding more than half of your audience due to a programming language choice is a poor decision.