ios - presentViewController 在 Swift 中不工作

Question

感谢您阅读本文。我想要一个函数 Swift 文件，我将项目的所有函数放入其中，其他 Swift 文件可以调用。我试图在函数文件中创建一个警报函数，当我传入一个特定的字符串时，它会显示一个特定的警报。当它在主文件中时它工作正常，但是当我将它移动到函数文件时，presentViewController 给我一个错误，说“使用未解析的标识符‘presentViewController’。”请帮忙!这是我的代码:在函数文件中:

import Foundation
import UIKit

/**********************************************
Variables
***********************************************/
var canTapButton: Bool = false
var tappedAmount = 0

/**********************************************
Functions
***********************************************/

//the alert to ask the user to assess their speed
func showAlert(alert: String) -> Void
{
if(alert == "pleaseAssessAlert")
{
    let pleaseAssessAlert = UIAlertController(title: "Welcome!", message: "If this is your firs time, I encourage you to use the Speed Assessment Tool (located in the menu) to figure which of you fingers is fastest!", preferredStyle: .Alert)
    //ok button
    let okButtonOnAlertAction = UIAlertAction(title: "Done", style: .Default)
        { (action) -> Void in
            //what happens when "ok" is pressed
    }
    pleaseAssessAlert.addAction(okButtonOnAlertAction)

    presentViewController(pleaseAssessAlert, animated: true, completion: nil)
}
else
{
    println("Error calling the alert function.")
}    
}

谢谢!

Answer 1

presentViewController是UIViewController的实例方法类(class)。所以你不能像这样在你的函数文件上访问它。

您应该像这样更改函数:

func showAlert(alert : String, viewController : UIViewController) -> Void
{
   if(alert == "pleaseAssessAlert")
   {
       let pleaseAssessAlert = UIAlertController(title: "Welcome!", message: "If this is your firs time, I encourage you to use the Speed Assessment Tool (located in the menu) to figure which of you fingers is fastest!", preferredStyle: .Alert)
       //ok button
       let okButtonOnAlertAction = UIAlertAction(title: "Done", style: .Default)
       { (action) -> Void in
            //what happens when "ok" is pressed
       }
       pleaseAssessAlert.addAction(okButtonOnAlertAction)
       viewController.presentViewController(pleaseAssessAlert, animated: true, completion: nil)
   }
   else
   {
       println("Error calling the alert function.")
   }    
}

在这里，您将 UIViewController 实例传递给此函数并调用该 View Controller 类的 presentViewController。