20 Essential Swift Extensions Every iOS Developer Must Know

Part 1: UIView Extensions - Making UI Development More Efficient

1. Adding Multiple Subviews at Once

How many times have you written multiple addSubview calls one after another? With this simple extension, you can add multiple subviews in just one function call!

extension UIView {
    func addSubviews(_ views: UIView...) {
        views.forEach { addSubview($0) }
    }
}

2. Pinning a View to its Superview

Setting up constraints to pin a view to its superview's edges is something we do often. This extension makes it easier with customizable insets.

extension UIView {
    func pinToSuperview(top: CGFloat = 0, left: CGFloat = 0,
                       bottom: CGFloat = 0, right: CGFloat = 0) {
        guard let superview = superview else {
            print("Error: superview does not exist")
            return
        }

        translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            topAnchor.constraint(equalTo: superview.topAnchor, constant: top),
            leftAnchor.constraint(equalTo: superview.leftAnchor, constant: left),
            bottomAnchor.constraint(equalTo: superview.bottomAnchor, constant: -bottom),
            rightAnchor.constraint(equalTo: superview.rightAnchor, constant: -right)
        ])
    }
}

3. Animation UIView

Extension to create UIView animations easily, including fade in and fade out effects.

extension UIView {
    /// Chain multiple animations with completion handler
    func animate(
        duration: TimeInterval,
        delay: TimeInterval = 0,
        options: UIView.AnimationOptions = [],
        animations: @escaping (UIView) -> Void,
        completion: ((Bool) -> Void)? = nil
    ) {
        UIView.animate(withDuration: duration, delay: delay,
                      options: options, animations: {
            animations(self)
        }, completion: completion)
    }

    /// Fade in view with customizable parameters
    func fadeIn(duration: TimeInterval = 0.3, delay: TimeInterval = 0,
               completion: ((Bool) -> Void)? = nil) {
        alpha = 0
        isHidden = false
        UIView.animate(withDuration: duration, delay: delay,
                      options: .curveEaseInOut, animations: {
            self.alpha = 1
        }, completion: completion)
    }

    /// Fade out view with customizable parameters
    func fadeOut(duration: TimeInterval = 0.3, delay: TimeInterval = 0,
                completion: ((Bool) -> Void)? = nil) {
        UIView.animate(withDuration: duration, delay: delay,
                      options: .curveEaseInOut, animations: {
            self.alpha = 0
        }, completion: { [weak self] finished in
            self?.isHidden = true
            completion?(finished)
        })
    }
}

// Multiple animations
view.animate(duration: 1.0) { view in
    view.transform = CGAffineTransform(scaleX: 1.5, y: 1.5)
}

// Fade out animation
view.fadeOut()

// Fade in animation
view.fadeIn()

4. Shake Animation for Error Feedback

A shake animation is a great way to provide visual feedback when validation fails.

extension UIView {
    func shake(duration: TimeInterval = 0.5, repeatCount: Float = 2) {
        let animation = CAKeyframeAnimation(keyPath: "transform.translation.x")
        animation.timingFunction = CAMediaTimingFunction(name: .linear)
        animation.duration = duration
        animation.values = [-10, 10, -8, 8, -5, 5, -3, 3, 0]
        animation.repeatCount = repeatCount
        layer.add(animation, forKey: "shake")
    }
}

if passwordTextField.text?.isEmpty ?? true {
    passwordTextField.shake()
    showError("Password cannot be empty")
}

5. Pulse Animation for Highlighting Elements

Need to highlight a specific UI element? This pulse animation is exactly what you need.

extension UIView {
    func pulse(duration: TimeInterval = 0.5, scale: CGFloat = 1.1) {
        UIView.animate(withDuration: duration / 2, animations: {
            self.transform = CGAffineTransform(scaleX: scale, y: scale)
        }, completion: { _ in
            UIView.animate(withDuration: duration / 2) {
                self.transform = CGAffineTransform.identity
            }
        })
    }
}

6. Rounded Corners for Specific Edges

Sometimes, you might want to round only specific corners of a view.

extension UIView {
    func roundCorners(corners: UIRectCorner, radius: CGFloat) {
        let path = UIBezierPath(
            roundedRect: bounds,
            byRoundingCorners: corners,
            cornerRadii: CGSize(width: radius, height: radius)
        )

        let mask = CAShapeLayer()
        mask.path = path.cgPath
        layer.mask = mask
    }
}

7. Adding Custom Shadows

Shadows can add depth and dimension to your UI, but setting them up often requires a lot of code.

extension UIView {
    func addShadow(
        color: UIColor = .black,
        opacity: Float = 0.3,
        offset: CGSize = CGSize(width: 0, height: 2),
        radius: CGFloat = 4
    ) {
        layer.shadowColor = color.cgColor
        layer.shadowOpacity = opacity
        layer.shadowOffset = offset
        layer.shadowRadius = radius
        layer.masksToBounds = false
    }
}

8. Easy Gradient Backgrounds

A gradient background can make your app look more visually appealing, and this extension makes it easy to implement.

extension UIView {
    func addGradient(
        colors: [UIColor],
        startPoint: CGPoint = CGPoint(x: 0.5, y: 0),
        endPoint: CGPoint = CGPoint(x: 0.5, y: 1)
    ) -> CAGradientLayer {
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = bounds
        gradientLayer.colors = colors.map { $0.cgColor }
        gradientLayer.startPoint = startPoint
        gradientLayer.endPoint = endPoint
        layer.insertSublayer(gradientLayer, at: 0)
        return gradientLayer
    }
}

let gradient = headerView.addGradient(
    colors: [.systemBlue, .systemIndigo],
    startPoint: CGPoint(x: 0, y: 0),
    endPoint: CGPoint(x: 1, y: 1)
)

9. Converting Views to Images

Need to capture a view as an image for sharing or further processing? This extension makes it simple.

extension UIView {
    func asImage() -> UIImage {
        let renderer = UIGraphicsImageRenderer(bounds: bounds)
        return renderer.image { rendererContext in
            layer.render(in: rendererContext.cgContext)
        }
    }
}

let chartImage = chartView.asImage()
// Now you can share this image via UIActivityViewController

10. Making Any View Touchable

This extension allows any view to respond to touch events using a simple closure-based approach.

extension UIView {
    func makeTouchable(action: @escaping () -> Void) {
        self.isUserInteractionEnabled = true
        let tap = TapGestureRecognizer(action: action)
        tap.numberOfTapsRequired = 1
        self.addGestureRecognizer(tap)
    }

    private class TapGestureRecognizer: UITapGestureRecognizer {
        private var action: () -> Void

        init(action: @escaping () -> Void) {
            self.action = action
            super.init(target: nil, action: nil)
            self.addTarget(self, action: #selector(self.execute))
        }

        @objc private func execute() {
            self.action()
        }
    }
}

infoIcon.makeTouchable {
    self.showInfoAlert()
}

Part 2: Swift Extensions - Productive Development Tools

11. Extension UICollectionView Setup

When working with UICollectionView, managing cells can become repetitive. This extension simplifies cell registration and dequeuing.

import UIKit

extension UICollectionView {
    func registerCellType(_ cellClass: T.Type) {
        let identifier = "\(cellClass)"
        let nib = UINib(nibName: identifier, bundle: Bundle(for: cellClass))
        register(nib, forCellWithReuseIdentifier: identifier)
    }

    func dequeueReusableCell(_ cellClass: T.Type,
                            for indexPath: IndexPath) -> T {
        let identifier = "\(cellClass)"
        guard let cell = dequeueReusableCell(withReuseIdentifier: identifier,
                                             for: indexPath) as? T else {
            fatalError("Error dequeueing cell")
        }
        return cell
    }
}

// Setup
private func setupView() {
    collectionView.dataSource = self
    collectionView.delegate = self
    collectionView.registerCellType(ScheduleTimeCollectionViewCell.self)
}

// DataSource
extension ViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView,
                       cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(
            ScheduleTimeCollectionViewCell.self,
            for: indexPath
        )
        return cell
    }
}

12. Extension UITableView Setup

Similar to UICollectionView, this extension simplifies UITableView setup.

import UIKit

extension UITableView {
    func registerNib(_ cell: T.Type) {
        let identifier = "\(cell)"
        register(UINib(nibName: String(describing: cell), bundle: nil),
                forCellReuseIdentifier: identifier)
    }

    func dequeueReusableCell(_ cell: T.Type,
                            for indexPath: IndexPath) -> T {
        let identifier = "\(cell)"
        guard let cell = dequeueReusableCell(withIdentifier: identifier,
                                             for: indexPath) as? T else {
            fatalError("Error dequeueing cell")
        }
        return cell
    }
}

private func setupTableView() {
    tableView.dataSource = self
    tableView.delegate = self
    tableView.registerNib(StudentTopDetailCell.self)
    tableView.registerNib(StudentMidDetailCell.self)
    tableView.registerNib(StudentBottomDetailCell.self)
    tableView.separatorStyle = .none
}

13. Extension String Validation

Ensuring user input is valid is crucial. This extension adds validation capabilities directly to the String type.

extension String {
    var isValidEmail: Bool {
        let regularExpression = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"
        let predicate = NSPredicate(format: "SELF MATCHES %@", regularExpression)
        return predicate.evaluate(with: self)
    }

    var isValidPhone: Bool {
        let regularExpression = "0[0-9]*"
        let predicate = NSPredicate(format: "SELF MATCHES %@", regularExpression)
        return predicate.evaluate(with: self)
    }

    var isValidPassword: Bool {
        let regularExpression = "(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])(?=.*?[#?!@$ %^&*-]).{8,}"
        let predicate = NSPredicate(format: "SELF MATCHES %@", regularExpression)
        return predicate.evaluate(with: self)
    }
}

func textFieldDidEndEditing(_ textField: UITextField) {
    switch type {
    case .email:
        if let text = textField.text, text.isEmpty || text.isValidEmail {
            resetError()
        } else {
            setError("Email is not valid")
        }
    case .password:
        if let text = textField.text, text.isEmpty || text.isValidPassword {
            resetError()
        } else {
            setError("Password must contain uppercase, lowercase, number and special character")
        }
    }
}

14. Extension Default String

Managing common string values like empty strings, spaces, and symbols becomes more consistent.

extension String {
    static var empty: String {
        return SC.empty
    }

    static var space: String {
        return SC.space
    }

    static var dash: String {
        return SC.dash
    }
}

typealias SC = StringConstants
enum StringConstants {
    static let empty = ""
    static let space = " "
    static let dash = "-"
}

// Empty variable
private(set) var id: String = .empty

// Optional handling
func set(student: ScheduleStudents) {
    self.id = student.id ?? .empty
}

// Spacing
totalStudentsLabel.text = total + SC.space + studentText

// Placeholder
field?.placeholder = .dash

15. Extension UIApplication Top Controller

Extension to find the topmost view controller that is currently active.

extension UIApplication {
    class func topViewController(_ viewController: UIViewController? =
                                 UIApplication.shared.currentActiveWindow?.rootViewController)
                                 -> UIViewController? {
        if let nav = viewController as? UINavigationController {
            return topViewController(nav.visibleViewController)
        }

        if let tab = viewController as? UITabBarController {
            if let selected = tab.selectedViewController {
                return topViewController(selected)
            }
        }

        if let presented = viewController?.presentedViewController {
            return topViewController(presented)
        }
        return viewController
    }

    var currentActiveWindow: UIWindow? {
        return UIApplication.shared.connectedScenes.flatMap {
            ($0 as? UIWindowScene)?.windows ?? []
        }.first { $0.isKeyWindow }
    }
}

private func presentPopup(message: String) {
    let popupViewController = PopoverToastViewController(message: message)
    popupViewController.modalPresentationStyle = .overCurrentContext
    UIApplication.topViewController()?.present(popupViewController, animated: true)
}

16. Extension Date Manipulation

Extension for easy Date manipulation.

extension Date {
    func dayOfWeek() -> Int {
        let calendar = Calendar.current
        let components = calendar.dateComponents([.weekday], from: self)
        return components.weekday!
    }

    func addMonth(n: Int) -> Date {
        let cal = NSCalendar.current
        return cal.date(byAdding: .month, value: n, to: self) ?? Date()
    }

    func addDay(n: Int) -> Date {
        let cal = NSCalendar.current
        return cal.date(byAdding: .day, value: n, to: self) ?? Date()
    }

    func addSec(n: Int) -> Date {
        let cal = NSCalendar.current
        return cal.date(byAdding: .second, value: n, to: self) ?? Date()
    }
}

// Day of week
let day = Date()
print(day.dayOfWeek()) // Thursday = 5

// Add month
@IBAction func nextButtonDidClick(_: UIButton) {
    baseDate = baseDate.addMonth(n: 1)
    monthLabel.text = dateFormatter.string(from: baseDate)
}

// Add seconds
let now = Date()
let futureDate = now.addSec(n: 120) // Add 2 minutes

17. Extension UIImage Base64

Convert images to Base64 strings for upload or API integrations.

extension UIImage {
    enum Format: String {
        case png
        case jpeg
    }

    func toBase64(type: Format = .jpeg, quality: CGFloat = 1,
                 addMimePrefix: Bool = false) -> String? {
        let imageData: Data?
        switch type {
        case .jpeg: imageData = jpegData(compressionQuality: quality)
        case .png: imageData = pngData()
        }
        guard let data = imageData else { return nil }

        let base64 = data.base64EncodedString()
        var result = base64.replacingOccurrences(of: "\"", with: "",
                                                 options: NSString.CompareOptions.literal,
                                                 range: nil)
        if addMimePrefix {
            let prefix = "data:image/\(type.rawValue);base64,"
            result = prefix + base64
        }
        return result
    }
}

func imageUploadButtonDidClick(image: UIImage?) {
    guard let image = image,
          let imageString = image.toBase64(addMimePrefix: true) else { return }
    // Upload imageString to server
}

18. Extension UITextField Add Done Button

Add a "Done" button to the keyboard for easy dismissal.

extension UITextField {
    func addDoneButton() {
        let doneToolbar = UIToolbar(frame: CGRect(x: 0, y: 0, width: 320, height: 50))
        doneToolbar.barStyle = UIBarStyle.default

        let flexSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace,
                                        target: nil, action: nil)
        let done = UIBarButtonItem(title: "Done", style: .done,
                                   target: self,
                                   action: #selector(self.doneButtonAction))

        var items = [UIBarButtonItem]()
        items.append(flexSpace)
        items.append(done)

        doneToolbar.items = items
        doneToolbar.sizeToFit()

        self.inputAccessoryView = doneToolbar
    }

    @objc func doneButtonAction() {
        self.endEditing(true)
    }
}

lazy var textField: UITextField = {
    let textField = UITextField()
    textField.addDoneButton() // Add done button
    textField.backgroundColor = .blue
    return textField
}()

19. Extension Converting Type

Simplify type conversions between Int, Double, and String.

extension Int {
    func toString() -> String {
        return String(describing: self)
    }
}

extension Double {
    func toString() -> String {
        return String(describing: self)
    }
}

extension String {
    func toInt() -> Int {
        return Int(self) ?? .zero
    }
}

// Int to String
let number = 42
let numberAsString = number.toString()

// Double to String
let pi = 3.14159
let piAsString = pi.toString()

// String to Int
let validNumber = "123"
let convertedNumber = validNumber.toInt()  // 123

20. Extension UIScrollView (To Top and Bottom)

Scroll to top or bottom programmatically with ease.

public extension UIScrollView {
    func scrollToBottom(animated: Bool, additionalBottomPadding: CGFloat = 0) {
        let bottomOffset = CGPoint(x: 0,
                                  y: contentSize.height - bounds.size.height +
                                     contentInset.bottom + additionalBottomPadding)
        setContentOffset(bottomOffset, animated: animated)
    }

    func scrollToTop() {
        let desiredOffset = CGPoint(x: 0, y: -contentInset.top)
        setContentOffset(desiredOffset, animated: true)
    }
}

// Scroll to top
var currentPage: Int = 1 {
    didSet {
        guard currentPage == 1 else { return }
        collectionView.scrollToTop()
    }
}

// Scroll to bottom when keyboard shows
@objc func keyboardWillShow(notification: NSNotification) {
    let keyboardHeight = tableView.getKeyboardHeight(notification: notification)
    tableView.scrollToBottom(animated: false,
                            additionalBottomPadding: keyboardHeight)
}

Conclusion