[swift-evolution] Add an ifPresent function to Optional

[Brian Pratt]

+1, feels like a no-brainer and is a nice low-impact change.

I like it.

On Fri, Mar 11, 2016 at 12:14 AM, Thorsten Seitz via swift-evolution <
swift-evolution at swift.org> wrote:

> +1
> ifPresent is something I've used a lot in Java/Guava.
> In Smalltalk we had at:ifPresent: for dictionary lookup which could then
> easily be simulated by lookup followed by ifPresent.
>
> -Thorsten
>
> Am 10.03.2016 um 22:55 schrieb Lammert Westerhoff via swift-evolution <
> swift-evolution at swift.org>:
>
> Currently the Swift Optional doesn’t have an ifPresent function.
> This function is much like the map function except that the passed in
> function always returns Void. Almost the same can be done with
> the mapfunction, however the map function gives a compiler warning if it's
> result is unused. Also a map function can be ambiguous when there are
> multiple functions with the same name. The ifPresent will always pick the
> right function; i.e. the one returning Void and therefore is not ambiguous .
>
> The ifPresent function is like the map function very powerful. Some
> examples of its usage:
>
> let mapView: MKMapView = ... // some map view
> let annotation: MKAnnotation? = ... // some optional annotation
> annotation.ifPresent(mapView.addAnnotation)
>
> I also wrote a Blog Post about this topic in which I present it as an
> extension of Optional with some more examples where I find it very useful:
> https://swiftforward.wordpress.com/2015/12/04/add-ifpresent-to-swift-optionals/
>
> The implementation can be as simple as following:
>
> public func ifPresent(@noescape f: (Wrapped) throws -> Void) rethrows {
>    _ = try map(f)
> }
>
> —
> Lammert Westerhoff
>
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