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From apocolipse <>
Subject [GitHub] thrift issue #1084: THRIFT-3773 Swift 3 Native Library
Date Wed, 07 Jun 2017 17:49:15 GMT
Github user apocolipse commented on the issue:
    Also, to anyone using this, I'm making a pretty decent sized change right now to how `TEnums`
work with Swift Enums.  Backstory is that Swift enums are overly opinionated and don't work
well if a new enum value is added to a service and the client hasn't updated.
    Other languages handle this pretty easily since enums are just Ints to them, they simply
read and store the value even if it doesn't match a case.  Since Swift's enums are finite
and opinionated, and not backed by Ints, this posed a bit of a challenge.  I initially designed
the TEnums to be RawRepresentable Int32 since it just made sense at the time, this let the
library handle read/write generically and the generator only needed to declare the cases and
an empty init case.  The problem arose when we saw it failing when new values came in.  Granted
it was designed to do so, but we needed a way internally to gracefully handle that.
    As a replacement, I'm removing the RawRepresentable/Int32 requirement on TEnums, and removing
the protocol read from the library as well, they will retain a rawValue and init(rawValue:)
to facilitate serialization and maintain compatibility with code that may be already using
those, but they're no longer inherently RawRepresentable.  The reason for this decision was
to add an `.unknown(Int32)` case that retains the extra value.  
    This is an opt-in case, so you'll need to use the generator flag `safe_enums`, but this
way you don't lose that information, and in the likely event you'll pull something that has
an unknown enum value and then need to send it back to a service, you'll retain the appropriate
value and maintain compatibility between server/client version mismatch.

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