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

[Adrian Zubarev]

Thats a good point!

Here is some bikeshedding:

public extension UIViewController {
      
    observe public var view: UIView {
          
        willSet {
            // do something useful here
        }
          
        didSet {
            // do something useful here
        }
    }
}
An extra observe keyword might signal to the compiler the correct intended usage.



-- 
Adrian Zubarev
Sent with Airmail

Am 8. Juli 2016 um 13:14:38, Leonardo Pessoa (me at lmpessoa.com) schrieb:

+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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