>> extension PropertyType
>> {
>> private static func create() -> Property<Self>
>> {
>> typealias SelfType = Self
>>
>> return Property<SelfType>.init()
>> }
>> }
>
> Oops, that's definitely a bug.
Excellent! I would also say that I have had a different error with…
private static func create() -> PropertyProtocol
{
return Property<Self>() // without the explicit .init
^ Non-associative operator is adjacent to operator of the
same precedence
^ No'>' candidates produce the expected contextual result
type 'PropertyProtocol'
}
So, it would seem that omitting the .init and using Self is interpreted
differently to using the .init and using Self. I'd hate you to solve one bug
just to find another for a very similar use case :-)
> 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.
Understood and somewhat expected. It's just that the error message is somewhat
distant from the error site and seemingly not connected.
>> 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`.
You'd have thought so wouldn't you. But although this works fine…
let childMirror = Mirror(reflecting: child.value)
print(child.label, child.value, childMirror.subjectType)
let subjectType = childMirror.subjectType
print(subjectType)
if let propertyType = subjectType as? PropertyType.Type
{
let property = PropertyFactory.createProperty(propertyType)
print(property)
}
… this doesn't…
let intType: Any.Type = Int.self
print(intType)
if let propertyType = intType as? PropertyType.Type // this cast fails
{
if var property = PropertyFactory.createProperty(propertyType) as?
Property<Int?>
{
property.value = 123
print(property)
}
}
>> 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…
Of course there will always be abusers of power but, by not permitting it, low
level framework code becomes more difficult, onerous and obfuscated to write.
Framework writers have always had to bear far more responsibility - think Cocoa
;-)
Joanna
--
Joanna Carter
Carter Consulting
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