+1.

> On Nov 15, 2016, at 19:53 , Jonathan Hull via swift-evolution 
> <[email protected]> wrote:
> 
> I would like to be able to get, at runtime, an array of all types conforming 
> to a particular protocol.  (Similarly, I would like to be able to get an 
> array of all subtypes of a given type).  Is this in the generics manifesto?  
> If not, can it be added?  What is the timeframe?
> 
> It seems to me, that the compiler should actually already have this 
> information, and it is just a matter of keeping it around when it is 
> requested.  I could be wrong about that though...
> 
> Why do I want this?  It would make a lot of things like plug-ins and 
> extensible factories possible (and much easier where they are possible).  For 
> example, you could add a new type to a factory (without the factory having to 
> be coupled to it) just by adhering to a protocol.  It would also make 
> building a swift version of NSCoding much easier.
> 
> I have asked for other, more complicated, language features (e.g. handler 
> funcs) to make those possible before, and I still want them (since I have 
> used them in other languages and it was enormously powerful), but I realized 
> that I should actually be able to make most of those features in a library 
> myself (albeit a bit slower than the compiler could) if I am able to get a 
> list of conforming types at runtime (and then call static methods on those 
> types).
> 
> Also, if there is a way to do this now (even if it is slow), I would 
> appreciate the help…
> 
> Thanks,
> Jon
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-- 
Rick Mann
[email protected]


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