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I have the following function working as I expect, in iOS 8:
func showConfirmBox(msg:String, title:String, firstBtnStr:String, secondBtnStr:String, caller:UIViewController) { let userPopUp = UIAlertController(title:title, message:msg, preferredStyle:UIAlertControllerStyle.Alert) userPopUp.addAction(UIAlertAction(title:firstBtnStr, style:UIAlertActionStyle.Default, handler:{action in})) userPopUp.addAction(UIAlertAction(title:secondBtnStr, style:UIAlertActionStyle.Default, handler:{action in})) caller.presentViewController(userPopUp, animated: true, completion: nil) } I would like to make something like the following, in order to pass as arguments the methods to be executed when one or the other of the buttons are going to be touched:
func showConfirmBox(msg:String, title:String, firstBtnStr:String, firstSelector:Selector, secondBtnStr:String, secondSelector:Selector, caller:UIViewController) { let userPopUp = UIAlertController(title:title, message:msg, preferredStyle:UIAlertControllerStyle.Alert) userPopUp.addAction(UIAlertAction(title:firstBtnStr, style:UIAlertActionStyle.Default, handler:{action in caller.firstSelector()})) userPopUp.addAction(UIAlertAction(title:secondBtnStr, style:UIAlertActionStyle.Default, handler:{action in caller.secondSelector()})) caller.presentViewController(userPopUp, animated: true, completion: nil) } Obviously I am not doing the right thing with firstSelector and secondSelector, because what I have tried up to now did not work. I suppose I am not using the right syntax for what I want, but I am sure it is possible to do what I would like to do. Any idea of the way to do it properly?
451
Function CallWhen calling a function with a function parameter, the value passed must be a pointer to a function. Use the function's name (without parentheses) for this: func(print); would call func , passing the print function to it.
Functions are data, and therefore can be passed around just like other values. This means a function can be passed to another function as an argument. This allows the function being called to use the function argument to carry out its action.
To assign function to a variable in Swift, declare a variable that takes specific set/type of parameters and return a specific type of value. Then we can assign a function that has same type of parameters and return value to this variable.
The Swift Programming Language guide has the following suggestion: “The use of external parameter names can allow a function to be called in an expressive, sentence-like manner, while still providing a function body that is readable and clear in intent.”
Oneword answer for your question is Closures
The Default Syntax for closures is () -> ()
Instead of Selector you could directly mention the method definition
func showConfirmBox(msg:String, title:String, firstBtnStr:String, firstSelector:(sampleParameter: String) -> returntype, secondBtnStr:String, secondSelector:() -> returntype, caller:UIViewController) { //Your Code } But using this will create readability problems so i suggest you to use typeAlias
typealias MethodHandler1 = (sampleParameter : String) -> Void typealias MethodHandler2 = () -> Void func showConfirmBox(msg:String, title:String, firstBtnStr:String, firstSelector:MethodHandler1, secondBtnStr:String, secondSelector:MethodHandler2) { // After any asynchronous call // Call any of your closures based on your logic like this firstSelector("FirstButtonString") secondSelector() } You can call your method like this
func anyMethod() { //Some other logic showConfirmBox(msg: "msg", title: "title", firstBtnStr: "btnString", firstSelector: { (firstSelectorString) in print(firstSelectorString) //this prints FirstButtonString }, secondBtnStr: "btnstring") { //Invocation comes here after secondSelector is called } } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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