[swift-evolution] [Pitch] Rename Mirror

Slava Pestov spestov at apple.com
Wed Aug 10 16:40:55 CDT 2016

> On Jul 21, 2016, at 4:06 PM, Anton Zhilin via swift-evolution <swift-evolution at swift.org> wrote:
> 2016-07-22 1:34 GMT+03:00 Dmitri Gribenko <gribozavr at gmail.com <mailto:gribozavr at gmail.com>>:
> > Mirror.DisplayStyle contains optional and set as special cases, but does not
> > contain function
> > Mirror collects all information possible at initialization, while for true
> > reflection we want laziness
> > Mirror allows customization. For example, Array<T> is represented with a
> > field for each of its elements. Do we want this for “true” reflection we
> > want to add in the future?
> Why can't we add these features to Mirror in future?
> Reflection in some other languages works as follows: we have a type (let's name it 'Reflection'). Each instance of it contains ID of one type and can, for example, retrieve an array of its static or normal methods.
> 'Mirror', on the other hand, serves as a container for information about a single instance. Moreover, types can completely customize contents of their 'Mirror's. This is incompatible with laziness and with how reflection should work, based on experience from other languages.

I think pointing a Mirror at a metatype value could be a good a mechanism for getting information about the type's stored properties and other members.

FWIW Mirrors are inspired by a feature of the same name in the Self language, which made reflection somewhat more principled than the disorganized APIs you see in Java and C#. Perhaps the latter are not a good model to follow here :-)


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