> On Mar 24, 2016, at 4:04 PM, Joanna Carter <joa...@carterconsulting.org.uk
> <mailto:joa...@carterconsulting.org.uk>> wrote:
>
> Unfortunately, this doesn't compile…
>
> extension PropertyType
> {
> private static func create() -> Property<Self>
> {
> return Property<Self>.init()
> ^ '>' is not a postfix unary operator
> }
> }
>
> Which is why I found it necessary to add a typealias like so…
>
> extension PropertyType
> {
> private static func create() -> Property<Self>
> {
> typealias SelfType = Self
>
> return Property<SelfType>.init()
> }
> }
Oops, that's definitely a bug.
> This doesn't compile either…
>
> struct PropertyFactory
> {
> static func createBoundPropertywithValueType(valueType: PropertyType.Type)
> -> PropertyProtocol
> {
> return valueType.create()
> ^ Member 'create' cannot be used on value of protocol type
> 'PropertyType'; use a generic constraint instead
> }
> }
>
> For some reason, as soon as you change the PropertyType extension static func
> to return PropertyProtocol…
>
> extension PropertyType
> {
> private static func create() -> PropertyProtocol
> {
> typealias SelfType = Self
>
> return Property<SelfType>.init()
> }
> }
>
> … then, and only then, the factory's method compiles correctly.
Oops, my fault, this one is by design. Since we're calling through a dynamic
type, our type system isn't able to express the result type
`Property<valueType>`, so we need to abstract it behind the PropertyProtocol.
> Of course, after all this effort, I still have the problem of how to get the
> Any.Type from the SubjectType property of a Mirror into a PropertyType.Type.
That one's easy, at least—you can take `Any.Type` and use `as?` to cast it to
`PropertyType.Type`.
> What would really make life easier here would be the ability to extend Any.
>
> Any chance?
I think that'd be cool. Some people fear the power (and ensuing responsibility)
that unleashes, though…
-Joe
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