How can you case-match on a function/closure stored in a variable?

Question

Consider this code:

func testA(){} func testB(value:Int){} func testC(value:String){} var someTest:Any = testA

How do you case-match on a variable holding a closure to find the correct one so you can call it?

switch someTest{ case let test where test:() -> Void: test() case let test where test:(value:Int) -> Void: test(4) case let test where test:(value:String) -> Void: test("A") }

Is something like this possible?

You want e.g case let test as (String) -> Void, compare stackoverflow.com/q/38980403/2976878 — Hamish
– Hamish, Commented Mar 11, 2018 at 17:22
Though depending on your use case, you may want to consider using an enum with associated values for each function type; then you can exhaustively switch without having to type-cast. — Hamish
– Hamish, Commented Mar 11, 2018 at 17:24
@Alexander: That Q&A does not cover matching against closures, I wonder if this is worth a separate answer (preferably from Hamish due to his initial comment) — Martin R
– Martin R, Commented Mar 11, 2018 at 18:13
Duh! as not where. Of course! Hamish, post that as an answer and I’ll accept it. — Mark A. Donohoe
– Mark A. Donohoe, Commented Mar 11, 2018 at 18:51

Mark A. Donohoe · Accepted Answer · 2018-03-11 20:31:41Z

Closure types are subject to the same switching patterns that any other types are:

switch someClosure { case let runnable as () -> Void: runnable() case let intConsumer as (Int) -> Void: intConsumer(4) case let stringConsumer as (String) -> Void: stringConsumer("A") }

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