如何创建可在多个ViewController中复用的Alert View？

Great question! Your current implementation is a solid start, but there are a few tweaks we can make to make it more reusable, idiomatic, and less error-prone for iOS development. Let's break this down step by step:

First: Fix the Issue in Your Current Code #

Your AlertView struct works in theory, but there's a critical mistake in how you're presenting the alert in your ViewController:

alert.present(alert, animated: true) { ... }

You can't call present(_:) on the alert itself—this method belongs to UIViewController. You need to call it on your ViewController instance instead. Also, using [weak self] in the completion closure helps avoid retain cycles. Here's the corrected call:

@IBAction func submitPressed(_ sender: Any) {
    let alertView = AlertView()
    let alert = alertView.showAlertBox(title: "Hours Added", message: "Hours have been updated")
    // Fix: Call present on self, not the alert
    self.present(alert, animated: true) { [weak self] in
        self?.dismiss(animated: true, completion: nil)
        self?.timeSubmitted = true
        self?.performSegue(withIdentifier: "unwindToMyHours", sender: nil)
    }
}

Better Reusable Approaches #

While your struct works after fixing the present call, we can optimize this for better reusability:

1. Use a UIViewController Extension (Most Idiomatic) #

Extending UIViewController lets any ViewController show alerts with a single method call, eliminating the need to create extra objects or handle presentation logic in every VC. This is the standard approach in iOS development:

import UIKit

extension UIViewController {
    // Basic alert with OK button and optional completion
    func showAlert(title: String, message: String, completion: (() -> Void)? = nil) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .cancel) { _ in
            completion?()
        })
        present(alert, animated: true)
    }
    
    // Overload for alerts with custom actions (e.g., OK + Cancel)
    func showAlert(title: String, message: String, actions: [UIAlertAction]) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        actions.forEach { alert.addAction($0) }
        present(alert, animated: true)
    }
}

Usage in your ViewController:

@IBAction func submitPressed(_ sender: Any) {
    showAlert(title: "Hours Added", message: "Hours have been updated") { [weak self] in
        self?.dismiss(animated: true)
        self?.timeSubmitted = true
        self?.performSegue(withIdentifier: "unwindToMyHours", sender: nil)
    }
}

2. Static Method in Your AlertView Struct #

If you prefer keeping alert logic in a dedicated struct, make the method static so you don't need to instantiate AlertView every time:

import UIKit

struct AlertView {
    static func showAlertBox(title: String, message: String) -> UIAlertController {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .cancel, handler: { _ in }))
        return alert
    }
}

Usage:

@IBAction func submitPressed(_ sender: Any) {
    let alert = AlertView.showAlertBox(title: "Hours Added", message: "Hours have been updated")
    self.present(alert, animated: true) { [weak self] in
        self?.dismiss(animated: true)
        self?.timeSubmitted = true
        self?.performSegue(withIdentifier: "unwindToMyHours", sender: nil)
    }
}

Key Takeaways #

• The UIViewController extension is the most convenient approach because it integrates directly with the ViewController lifecycle and reduces boilerplate.
• Always use [weak self] in completion closures to prevent memory leaks.
• Your original implementation was almost correct—fixing the presentation call and making the method static (or using an extension) makes it fully reusable across all ViewControllers.

内容的提问来源于stack exchange，提问作者user15554941