[swift-evolution] [Discussion] Allow injection of `didSet` and `willSet`

[Leonardo Pessoa]

+1. This would allow us to create observers on any foreign variable. I'm
far from a compiler right now but I wouldn't this syntax create a new
variable instead of observing an existing one? Even if not, by reading
this one could be mislead to believe so. Perhaps you should give it
something to differentiate from creating a new var, for example by
suppressing the type on this declaration.

On Friday, 8 July 2016, Adrian Zubarev via swift-evolution <
swift-evolution at swift.org> wrote:

> Hello dear Swift community, I’m not sure if this was discussed before or
> not, but I really want to know if something like this is welcome for the
> future Swift version. If this topic was already discussed, I’m apologizing
> for bringing it back to life in a new thread.
>
> Lets say I’ve got a third party module and I want to know when the a
> variable of some type has changed:
>
> extension UIViewController {
>
>     public override var view: UIView {
>
>         willSet {
>             // do something useful here
>         }
>
>         didSet {
>             // do something useful here
>         }
>     }
> }
>
> Wouldn’t be handy to inject custom didSet and willSet functions into any
> property or computed property?
>
> This would also allow us to build a proper two-way-binding mechanism.
>
>
>
> --
> Adrian Zubarev
> Sent with Airmail
>
>

-- 
L
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