快速传递带有参数作为参数的闭包

Question

So the idea is to make a general purpose alert creator that I can pass a completion handler to....

 static func makeTextFieldAlert(msg:String, title:String, onOk: @escaping (_ newText:String) -> Void ) -> UIAlertController {
        let alertController = UIAlertController(title: "Add New Name", message: "", preferredStyle: UIAlertController.Style.alert)

        let saveAction = UIAlertAction(title: "Save", style: UIAlertAction.Style.default, handler: { alert -> Void in
            let firstTextField = alertController.textFields![0] as UITextField
            onOk(firstTextField.text!)
        })

However.....xcode forces me to put the _ there and it forces me to put @escaping there....

And....when I try to call this whole mess....It won't even compile:

@IBAction func click(_ sender: Any) {
        print("here")
        let newThing:UIAlertController = Util.makeTextFieldAlert(msg: "Yes", title: "Create Thing", onOk:{_ in
            ThingUtil.createThing(thing: newText)
        } )

So I try $0 in place of newText and I get

"Anonymous closure arguments cannot be used inside a closure that has explicit arguments"

And I try what I have above and I get:

Use of unresolved identifier 'newText'

I would prefer to just use the variable newText for the sake of clarity....but at this point, I just want it to compile. What am I doing wrong? Thank you!

Answer 1

This "thing" is compiling at my end:

class Util {
    static func makeTextFieldAlert(msg:String, title:String, onOk: @escaping (_ newText:String) -> Void ) -> UIAlertController {
        let alertController = UIAlertController(title: "Add New Name", message: "", preferredStyle: UIAlertController.Style.alert)

        let saveAction = UIAlertAction(title: "Save", style: UIAlertAction.Style.default, handler: { alert -> Void in
            let firstTextField = alertController.textFields![0] as UITextField
            onOk(firstTextField.text!)
        })
        alertController.addAction(saveAction)
        return alertController
    }
}


class ViewController: UIViewController {


    @IBAction func click(_ sender: Any) {
        print("here")
        let newThing:UIAlertController = Util.makeTextFieldAlert(msg: "Yes", title: "Create Thing", onOk:{ newText in
            print(newText)
        } )
        present(newThing, animated: true, completion: nil)
    }

}

May be the problem is this ThingUtil.createThing(thing: newText) . Are you sure it takes a string argument?

This should be your ThingUtil class API

class ThingUtil {
    static func createThing(thing:String) {

    }
}