[swift-evolution] Proposal: Expose getter/setters in the same way as regular methods

Marc Knaup marc at knaup.koeln
Sun Dec 13 18:49:03 CST 2015

Wait, where is stated that KVO is a long-term goal for Swift? I might have
missed that.

I find that one of Objective-C's most annoying features. It makes it really
difficult to reason about code when things can happen unexpectedly left and
right. It's the same issue with aspect-oriented programming.

I prefer explicit integration points like closures, delegates and alike.
Most times I used KVO in the past was to work around bugs or annoyances on
iOS, like for example forcing a button stay enabled even when iOS disables

Also it's unlikely that all mutable properties will support observation
automatically. That would require the optimizer to keep using dynamic
dispatch for all of them which will hurt performance.

But I'm getting off-topic since your discussion is not about KVO nor about

Being able to refer to getters and setters is a good idea and aligns with
being able to refer to initializers and methods.
I would also add subscripts to the list if possible.

On Mon, Dec 14, 2015 at 1:34 AM, Michael Henson via swift-evolution <
swift-evolution at swift.org> wrote:

> Swift-like full KVO/KVC as in Objective-C is a stated long-term goal for
> Swift's evolution. The 90% solution might be more straightforward:
> class Example {
>   var member: String
>   func print() {
>     print(self.member)
>   }
> }
> var example = Example(member: "Hi!")
> var example_print_method = example.print
> example_print_method()
> result:
> Hi!
> If there were a mechanism for referring to the getter and setter methods
> on the var member property as the same kind of self-capturing closures, it
> could make simple cases of data binding easier to implement:
> var serializeFields = [
>   "member": example.member#get,
> ]
> var deserializeFields = [
>   "member": example.member#set,
> ]
> var broadcastValueTo = [
>   "memberValues": [
>      example.member#set,
>      example2.member#set,
>      example3.member#set,
>   ]
> ]
> viewController.textField.onValueChanged(example.member#set)
> Etc.
> The "#" notation is just a placeholder for "whatever mechanism is decided
> upon", though it does seem to be available and using it postfix makes a
> first-glance sense to me in terms of the semantics of expressions.
> Mike
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
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