在Swift中将函数作为参数传递 [英] Passing functions as parameters in Swift

问题描述

在iOS 8中，我可以正常使用以下功能:

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)
}

我想进行如下操作，以便将要触摸一个或另一个按钮时要执行的方法作为参数传递:

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)
}

很明显，我在firstSelector和secondSelector上做的不是正确的事情，因为到目前为止我尝试过的工作都不起作用.我想我没有为我想要的使用正确的语法，但是我确信可以做自己想做的事情.对正确执行方法有任何想法吗?

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?

推荐答案

您的问题的一个答案是

Oneword answer for your question is Closures

闭包的默认语法为() -> ()

您可以直接提及方法定义，而不是选择器

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
}

但是使用它会产生可读性问题，所以我建议您使用typeAlias

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()
}

您可以像这样调用您的方法

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

         }
}

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