UIAlertController as Action Sheet

Action sheets in UIKit provide a modal interface to present users with a set of options related to a specific action or context. They are implemented using UIAlertController with the .actionSheet style, offering a native, touch-friendly way to display choices like confirming an action, selecting an option, or canceling.

Purpose

• User Choices: Present multiple options in a concise, modal interface.
• Contextual Actions: Offer actions tied to a specific UI element or user interaction.
• Native Look: Provide a system-standard UI that adapts to iPhone and iPad layouts.

UIKit Implementation

Action sheets are created using UIAlertController with the preferredStyle set to .actionSheet.

Key Components

• UIAlertController: The controller managing the action sheet.
• UIAlertAction: Individual actions (buttons) with titles, styles, and handlers.
• Popover Configuration: Required for iPad to anchor the action sheet.

Basic Example

import UIKit

class ViewController: UIViewController {
    @IBAction func showActionSheet(_ sender: UIButton) {
        let alertController = UIAlertController(title: "Options", message: "Choose an action", preferredStyle: .actionSheet)
        
        let action1 = UIAlertAction(title: "Edit", style: .default) { _ in
            print("Edit selected")
        }
        let action2 = UIAlertAction(title: "Delete", style: .destructive) { _ in
            print("Delete selected")
        }
        let cancel = UIAlertAction(title: "Cancel", style: .cancel) { _ in
            print("Cancelled")
        }
        
        alertController.addAction(action1)
        alertController.addAction(action2)
        alertController.addAction(cancel)
        
        // iPad popover configuration
        if let popoverController = alertController.popoverPresentationController {
            popoverController.sourceView = sender
            popoverController.sourceRect = sender.bounds
            popoverController.permittedArrowDirections = .any
        }
        
        present(alertController, animated: true, completion: nil)
    }
}

Key Points

• Styles: UIAlertAction supports .default (standard actions), .destructive (for actions like delete), and .cancel (typically one cancel action).
• Popover (iPad): Configure popoverPresentationController to anchor the action sheet on iPad.
• Title/Message: Optional title and message provide context but should be concise.
• Presentation: Present modally using present(_:animated:completion:).

Advanced Features

Dynamic Actions

Dynamically add actions based on context:

let alertController = UIAlertController(title: "Options", message: nil, preferredStyle: .actionSheet)
if canEdit {
    alertController.addAction(UIAlertAction(title: "Edit", style: .default) { _ in print("Edit") })
}
alertController.addAction(UIAlertAction(title: "Delete", style: .destructive) { _ in print("Delete") })
alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel))

Customizing Appearance

Limited customization is possible via UIAlertController properties:

alertController.view.tintColor = .systemBlue // Change button tint

Enabling/Disabling Actions

Disable actions dynamically by setting the isEnabled property:

let action = UIAlertAction(title: "Edit", style: .default) { _ in print("Edit") }
action.isEnabled = canEdit
alertController.addAction(action)

iPad Popover Anchoring

Always configure popoverPresentationController for iPad:

if let popoverController = alertController.popoverPresentationController {
    popoverController.sourceView = view // Anchor to a view
    popoverController.sourceRect = view.bounds
}

Best Practices

• Conciseness: Limit actions to 3–5 options to avoid overwhelming users.
• Clarity: Use clear, action-oriented titles (e.g., “Delete” instead of “Remove Item”).
• Cancel Action: Always include a .cancel action to allow users to dismiss the sheet.
• Accessibility: Ensure actions are VoiceOver-compatible with descriptive titles.
• Testing: Test on iPhone and iPad to verify presentation and popover behavior.
• Context: Use action sheets for contextual choices, not for alerts (use .alert style instead).

Limitations

• Customization: Action sheets have limited visual customization to maintain system consistency.
• iPad Popovers: Requires manual popover configuration for iPad.
• Modal Nature: Action sheets interrupt the user flow, so use sparingly for critical choices.
• Single Cancel: Only one .cancel action is supported, automatically placed at the bottom.

Summary

Action sheets in UIKit, implemented via UIAlertController with .actionSheet style, provide a native, modal interface for presenting user options. They support dynamic actions, destructive styles, and iPad popover configurations. By following best practices, developers can create intuitive and accessible action sheets that enhance the user experience in UIKit-based apps.