create alert function in all view controllers - sw

问题:

I'm trying to declare a function for showing alerts in my app. To avoid repeating work, i'm trying to use same function for all my app. I tried to do that by creating a class with function showNotification. but when i create an object of that class and call the method, nothing happens. How can i do that?

class SharedPropertiesAndMetods : UIViewController {

    func showNotification(title: String, message: String)
    {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let defaultAction = UIAlertAction(title: "تائید", style: .default, handler: nil)
        alertController.addAction(defaultAction)
        present(alertController, animated: true, completion: nil)
    }

}

回答1:

What I would do is to create a 'generic' view controller that do the job and than inherit from it:

1. If you want to display alert each time view did appear:

class GenericViewController: UIViewController {

    // MARK: - View lifecycle -

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        if let notification = self.shouldDisplayAlertNotification() {
            self.showNotification(notification)
        }
    }

    // MARK: - Internal methods -

    func shouldDisplayAlertNotification() -> AlertNotification? {
        return nil
    }

    // MARK: - Private methods -

    private func showNotification(_ alertNotification: AlertNotification) {
    }

}

class MyController: GenericViewController {

    override func shouldDisplayAlertNotification() -> AlertNotification? {
        return AlertNotification(title: "Title", message: "Message")
    }

}

Where AlertNotification is your custom model class:

class AlertNotification {
    var title: String
    var message: String

    init(title: String, message: String) {
        self.title = title
        self.message = message
    }
}

In this way, only VC that overrides shouldDisplayAlertNotificationwill display alert.

2. If you want to display alert on 'demand':

As suggested, extend UIViewController

extension UIViewController {
    func showNotification(title: String, message: String) {
    }
}

回答2:

Actually you can declare a simple method anywhere outside class.

func showAlertWithCompletion(message:String,okTitle:String,cancelTitle:String?,completionBlock:@escaping (_ okPressed:Bool)->()){
    let alertController = UIAlertController(title: AppName, message: message, preferredStyle: .alert)
    let okAction = UIAlertAction(title: okTitle, style: .default) { (ok) in
        completionBlock(true)
    }
    alertController.addAction(okAction)
    if let cancelTitle = cancelTitle{
        let cancelOption = UIAlertAction(title: cancelTitle, style: .cancel, handler: { (axn) in
            completionBlock(false)

        })
        alertController.addAction(cancelOption)
    }

    if let topController = UIWindow.topViewController(){
      topController.present(alertController, animated: true, completion: nil)
    }

}

This way wherever you call it, you will get ok button pressed callback in completion handle or even make Extension as described by @Ganesh Kumar

回答3:

Use an extension like this

extension UIViewController {
  func showAlert(title: String, message: String) {
    let alertController = UIAlertController(title: title, message:
      message, preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: {action in
    }))
    self.present(alertController, animated: true, completion: nil)
  }
}

call the function like this

self.showAlert(title: "hi", message: "test")

回答4:

Why not just an extension

extension UIViewController {

    func showNotification(title: String, message: String)
    {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let defaultAction = UIAlertAction(title: "تائید", style: .default, handler: nil)
        alertController.addAction(defaultAction)
        present(alertController, animated: true, completion: nil)
    }
}

回答5:

You can also create one util file in your app, in that you can add any reusable method or function and use it anywhere in your app Like,

import Foundation import UIKit

//MARK: - ALERT

func showMessage(title: String, message: String!, VC: UIViewController) {

let alert : UIAlertController = UIAlertController(title: "", message: message, preferredStyle: UIAlertControllerStyle.alert)
let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default) {
    UIAlertAction in
}
alert.addAction(okAction)
VC.present(alert, animated: true, completion: nil)

}

回答6:

You could create extension to alertController and also have option for action handler. This will allow to use two different Alert controller based on handler is required or not.

extension  UIAlertControler {

class func genericErrorAlert(forAlert message: String, completion: ((UIAlertAction) -> Void)? = nil )

    let alert = UIAlertController(title: "Error", message: message, preferredStyle: .alert)

    alert.addAction(UIAlertAction(title: "OK", style: .cancel, handler: completion))

    return alert
  }
}