Pass "function with parameter" as parameter

Question

This doesn't compile

func showAlert(_ title: String, message: String, onOk: (()->())? = nil, onAnotherAction:((anotherActionTitle : String)-> Void)? = nil) { let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert) let ok = UIAlertAction(title: "OK", style: .default) { (action) in onOk?() } let anotherAction = UIAlertAction(title: anotherActionTitle, style: .default) { (action) in onAnotherAction?() } alertController.addAction(ok) alertController.addAction(anotherAction) ... }

This compiles

func showAlert(_ title: String, message: String, onOk: (()->())? = nil, onAnotherAction:((String)-> Void)? = nil)

However, I have to declare another parameter for the title anotherActionTitle of onAnotherAction().

Is there a way make the first approach work? Thanks!

matt · Accepted Answer · 2018-12-30 22:30:51Z

However, I have to declare another parameter for the title anotherActionTitle of onAnotherAction()

No, you don't have to do that. Just make it a normal parameter of the function as a whole:

func showAlert(_ title: String, message: String, onOk: (()->())? = nil, anotherActionTitle: String? = nil, onAnotherAction: (()->())? = nil) {

The rest of your function will then compile and work correctly.

Daniel Hall · Accepted Answer · 2018-12-30 18:59:45Z

Since the implementation of SE-0111 as part of Swift 3, it is no longer possible to have named parameters for closure types.

There is a conceptual roadmap that the Swift core team has laid out for restoring named closure parameters at some point in the future, but no timeline for implementation that I am aware of:

https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160711/024331.html

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